Artery

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https://en.wikipedia.org/wiki/Artery

 

Artery
Diagram of an artery
Details
Identifiers
Latin	Arteria (plural: arteriae)
MeSH	D001158
TA98	A12.0.00.003 A12.2.00.001
TA2	3896
FMA	50720

An artery (PL: arteries) (from Greek ἀρτηρία (artēríā) 'windpipe, artery') is a blood vessel in humans and most other animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pulmonary and the umbilical arteries, which carry deoxygenated blood to the organs that oxygenate it (lungs and placenta, respectively). The effective arterial blood volume is that extracellular fluid which fills the arterial system.

The arteries are part of the circulatory system, that is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, the maintenance of optimum blood pH, and the circulation of proteins and cells of the immune system.

Arteries contrast with veins, which carry blood back towards the heart.

Structure

Microscopic anatomy of an artery.

Cross-section of a human artery

See also: Arterial tree

The anatomy of arteries can be separated into gross anatomy, at the macroscopic level, and microanatomy, which must be studied with a microscope. The arterial system of the human body is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs.

The outermost layer of an artery (or vein) is known as the tunica externa, also known as tunica adventitia, and is composed of collagen fibers and elastic tissue - with the largest arteries containing vasa vasorum (small blood vessels that supply large blood vessels). Most of the layers have a clear boundary between them, however the tunica externa has a boundary that is ill-defined. Normally its boundary is considered when it meets or touches the connective tissue. Inside this layer is the tunica media, or media, which is made up of smooth muscle cells, elastic tissue (also called connective tissue proper) and collagen fibres. The innermost layer, which is in direct contact with the flow of blood, is the tunica intima, commonly called the intima. The elastic tissue allows the artery to bend and fit through places in the body. This layer is mainly made up of endothelial cells (and a supporting layer of elastin rich collagen in elastic arteries). The hollow internal cavity in which the blood flows is called the lumen.

Development

Further information: Angiogenesis and Vasculogenesis

Arterial formation begins and ends when endothelial cells begin to express arterial specific genes, such as ephrin B2.

Function

Arteries form part of the human circulatory system

Main article: Circulatory system

Arteries form part of the circulatory system. They carry blood that is oxygenated after it has been pumped from the heart. Coronary arteries also aid the heart in pumping blood by sending oxygenated blood to the heart, allowing the muscles to function. Arteries carry oxygenated blood away from the heart to the tissues, except for pulmonary arteries, which carry blood to the lungs for oxygenation (usually veins carry deoxygenated blood to the heart but the pulmonary veins carry oxygenated blood as well). There are two types of unique arteries. The pulmonary artery carries blood from the heart to the lungs, where it receives oxygen. It is unique because the blood in it is not "oxygenated", as it has not yet passed through the lungs. The other unique artery is the umbilical artery, which carries deoxygenated blood from a fetus to its mother.

Arteries have a blood pressure higher than other parts of the circulatory system. The pressure in arteries varies during the cardiac cycle. It is highest when the heart contracts and lowest when heart relaxes. The variation in pressure produces a pulse, which can be felt in different areas of the body, such as the radial pulse. Arterioles have the greatest collective influence on both local blood flow and on overall blood pressure. They are the primary "adjustable nozzles" in the blood system, across which the greatest pressure drop occurs. The combination of heart output (cardiac output) and systemic vascular resistance, which refers to the collective resistance of all of the body's arterioles, are the principal determinants of arterial blood pressure at any given moment.

Arteries have the highest pressure and have narrow lumen diameter. It consists of three tunics: Tunica media, intima, and external.

Systemic arteries are the arteries (including the peripheral arteries), of the systemic circulation, which is the part of the cardiovascular system that carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart. Systemic arteries can be subdivided into two types—muscular and elastic—according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina. The larger arteries (>10  mm diameter) are generally elastic and the smaller ones (0.1–10 mm) tend to be muscular. Systemic arteries deliver blood to the arterioles, and then to the capillaries, where nutrients and gases are exchanged.

After traveling from the aorta, blood travels through peripheral arteries into smaller arteries called arterioles, and eventually to capillaries. Arterioles help in regulating blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.

Aorta

Aorta is the largest blood vessel in human body

The aorta is the root systemic artery (i.e., main artery). In humans, it receives blood directly from the left ventricle of the heart via the aortic valve. As the aorta branches and these arteries branch, in turn, they become successively smaller in diameter, down to the arterioles. The arterioles supply capillaries, which in turn empty into venules. The first branches off of the aorta are the coronary arteries, which supply blood to the heart muscle itself. These are followed by the branches of the aortic arch, namely the brachiocephalic artery, the left common carotid, and the left subclavian arteries.

Capillaries

Main article: Capillaries

The capillaries are the smallest of the blood vessels and are part of the microcirculation. The microvessels have a width of a single cell in diameter to aid in the fast and easy diffusion of gases, sugars and nutrients to surrounding tissues. Capillaries have no smooth muscle surrounding them and have a diameter less than that of red blood cells; a red blood cell is typically 7 micrometers outside diameter, capillaries typically 5 micrometers inside diameter. The red blood cells must distort in order to pass through the capillaries.

These small diameters of the capillaries provide a relatively large surface area for the exchange of gases and nutrients.

Clinical significance

Diagram showing the effects of atherosclerosis on an artery.

Systemic arterial pressures are generated by the forceful contractions of the heart's left ventricle. High blood pressure is a factor in causing arterial damage. Healthy resting arterial pressures are relatively low, mean systemic pressures typically being under 100 mmHg (1.9 psi; 13 kPa) above surrounding atmospheric pressure (about 760 mmHg, 14.7 psi, 101 kPa at sea level). To withstand and adapt to the pressures within, arteries are surrounded by varying thicknesses of smooth muscle which have extensive elastic and inelastic connective tissues. The pulse pressure, being the difference between systolic and diastolic pressure, is determined primarily by the amount of blood ejected by each heart beat, stroke volume, versus the volume and elasticity of the major arteries.

A blood squirt also known as an arterial gush is the effect when an artery is cut due to the higher arterial pressures. Blood is spurted out at a rapid, intermittent rate, that coincides with the heartbeat. The amount of blood loss can be copious, can occur very rapidly, and be life-threatening.

Over time, factors such as elevated arterial blood sugar (particularly as seen in diabetes mellitus), lipoprotein, cholesterol, high blood pressure, stress and smoking, are all implicated in damaging both the endothelium and walls of the arteries, resulting in atherosclerosis. Atherosclerosis is a disease marked by the hardening of arteries. This is caused by an atheroma or plaque in the artery wall and is a build-up of cell debris, that contain lipids, (cholesterol and fatty acids), calcium and a variable amount of fibrous connective tissue.

Accidental intraarterial injection either iatrogenically or through recreational drug use can cause symptoms such as intense pain, paresthesia and necrosis. It usually causes permanent damage to the limb; often amputation is necessary.

History

Further information: Circulatory system § History

Among the Ancient Greeks before Hippocrates, all blood vessels were called Φλέβες, phlebes. The word arteria then referred to the windpipe. Herophilos was the first to describe anatomical differences between the two types of blood vessel. While Empedocles believed that the blood moved to and fro through the blood vessels, there was no concept of the capillary vessels that join arteries and veins, and there was no notion of circulation. Diogenes of Apollonia developed the theory of pneuma, originally meaning just air but soon identified with the soul itself, and thought to co-exist with the blood in the blood vessels. The arteries were thought to be responsible for the transport of air to the tissues and to be connected to the trachea. This was as a result of finding the arteries of cadavers devoid of blood.

In medieval times, it was supposed that arteries carried a fluid, called "spiritual blood" or "vital spirits", considered to be different from the contents of the veins. This theory went back to Galen. In the late medieval period, the trachea, and ligaments were also called "arteries".

William Harvey described and popularized the modern concept of the circulatory system and the roles of arteries and veins in the 17th century.

Alexis Carrel at the beginning of the 20th century first described the technique for vascular suturing and anastomosis and successfully performed many organ transplantations in animals; he thus actually opened the way to modern vascular surgery that was previously limited to vessels' permanent ligation.

Military engineering

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Military_engineering

Military engineer training in Ukraine, 2017

Military engineering is loosely defined as the art, science, and practice of designing and building military works and maintaining lines of military transport and military communications. Military engineers are also responsible for logistics behind military tactics. Modern military engineering differs from civil engineering. In the 20th and 21st centuries, military engineering also includes CBRN defense and other engineering disciplines such as mechanical and electrical engineering techniques.

According to NATO, "military engineering is that engineer activity undertaken, regardless of component or service, to shape the physical operating environment. Military engineering incorporates support to maneuver and to the force as a whole, including military engineering functions such as engineer support to force protection, counter-improvised explosive devices, environmental protection, engineer intelligence and military search. Military engineering does not encompass the activities undertaken by those 'engineers' who maintain, repair and operate vehicles, vessels, aircraft, weapon systems and equipment."

Military engineering is an academic subject taught in military academies or schools of military engineering. The construction and demolition tasks related to military engineering are usually performed by military engineers including soldiers trained as sappers or pioneers. In modern armies, soldiers trained to perform such tasks while well forward in battle and under fire are often called combat engineers.

In some countries, military engineers may also perform non-military construction tasks in peacetime such as flood control and river navigation works, but such activities do not fall within the scope of military engineering.

Etymology

The word engineer was initially used in the context of warfare, dating back to 1325 when engine’er (literally, one who operates an engine) referred to "a constructor of military engines". In this context, "engine" referred to a military machine, i. e., a mechanical contraption used in war (for example, a catapult).

As the design of civilian structures such as bridges and buildings developed as a technical discipline, the term civil engineering entered the lexicon as a way to distinguish between those specializing in the construction of such non-military projects and those involved in the older discipline. As the prevalence of civil engineering outstripped engineering in a military context and the number of disciplines expanded, the original military meaning of the word "engineering" is now largely obsolete. In its place, the term "military engineering" has come to be used.

History

Aerial view of Mulberry harbour "B" (27 October 1944)

In ancient times, military engineers were responsible for siege warfare and building field fortifications, temporary camps and roads. The most notable engineers of ancient times were the Romans and Chinese, who constructed huge siege-machines (catapults, battering rams and siege towers). The Romans were responsible for constructing fortified wooden camps and paved roads for their legions. Many of these Roman roads are still in use today.

The first civilization to have a dedicated force of military engineering specialists were the Romans, whose army contained a dedicated corps of military engineers known as architecti. This group was pre-eminent among its contemporaries. The scale of certain military engineering feats, such as the construction of a double-wall of fortifications 30 miles (48 km) long, in just 6 weeks to completely encircle the besieged city of Alesia in 52 B.C.E., is an example. Such military engineering feats would have been completely new, and probably bewildering and demoralizing, to the Gallic defenders. Vitruvius is the best known of these Roman army engineers, due to his writings surviving.

Examples of battles before the early modern period where military engineers played a decisive role include the Siege of Tyre under Alexander the Great, the Siege of Masada by Lucius Flavius Silva as well as the Battle of the Trench under the suggestion of Salman the Persian to dig a trench.

For about 600 years after the fall of the Roman empire, the practice of military engineering barely evolved in the west. In fact, much of the classic techniques and practices of Roman military engineering were lost. Through this period, the foot soldier (who was pivotal to much of the Roman military engineering capability) was largely replaced by mounted soldiers. It was not until later in the Middle Ages, that military engineering saw a revival focused on siege warfare.

Military engineers planned castles and fortresses. When laying siege, they planned and oversaw efforts to penetrate castle defenses. When castles served a military purpose, one of the tasks of the sappers was to weaken the bases of walls to enable them to be breached before means of thwarting these activities were devised. Broadly speaking, sappers were experts at demolishing or otherwise overcoming or bypassing fortification systems.

Working dress of the Royal Military Artificers in Gibraltar, 1795

With the 14th-century development of gunpowder, new siege engines in the form of cannons appeared. Initially military engineers were responsible for maintaining and operating these new weapons just as had been the case with previous siege engines. In England, the challenge of managing the new technology resulted in the creation of the Office of Ordnance around 1370 in order to administer the cannons, armaments and castles of the kingdom. Both military engineers and artillery formed the body of this organization and served together until the office's successor, the Board of Ordnance was disbanded in 1855.

In comparison to older weapons, the cannon was significantly more effective against traditional medieval fortifications. Military engineering significantly revised the way fortifications were built in order to be better protected from enemy direct and plunging shot. The new fortifications were also intended to increase the ability of defenders to bring fire onto attacking enemies. Fort construction proliferated in 16th-century Europe based on the trace italienne design.

French sappers during the Battle of Berezina in 1812

By the 18th century, regiments of foot (infantry) in the British, French, Prussian and other armies included pioneer detachments. In peacetime these specialists constituted the regimental tradesmen, constructing and repairing buildings, transport wagons, etc. On active service they moved at the head of marching columns with axes, shovels, and pickaxes, clearing obstacles or building bridges to enable the main body of the regiment to move through difficult terrain. The modern Royal Welch Fusiliers and French Foreign Legion still maintain pioneer sections who march at the front of ceremonial parades, carrying chromium-plated tools intended for show only. Other historic distinctions include long work aprons and the right to wear beards. In West Africa, the Ashanti army was accompanied to war by carpenters who were responsible for constructing shelters and blacksmiths who repaired weapons. By the 18th century, sappers were deployed in the Dahomeyan army during assaults against fortifications.

The Peninsular War (1808–14) revealed deficiencies in the training and knowledge of officers and men of the British Army in the conduct of siege operations and bridging. During this war low-ranking Royal Engineers officers carried out large-scale operations. They had under their command working parties of two or three battalions of infantry, two or three thousand men, who knew nothing in the art of siegeworks. Royal Engineers officers had to demonstrate the simplest tasks to the soldiers, often while under enemy fire. Several officers were lost and could not be replaced, and a better system of training for siege operations was required. On 23 April 1812 an establishment was authorised, by Royal Warrant, to teach "Sapping, Mining, and other Military Fieldworks" to the junior officers of the Corps of Royal Engineers and the Corps of Royal Military Artificers, Sappers and Miners.

The first courses at the Royal Engineers Establishment were done on an all ranks basis with the greatest regard to economy. To reduce staff the NCOs and officers were responsible for instructing and examining the soldiers. If the men could not read or write they were taught to do so, and those who could read and write were taught to draw and interpret simple plans. The Royal Engineers Establishment quickly became the centre of excellence for all fieldworks and bridging. Captain Charles Pasley, the director of the Establishment, was keen to confirm his teaching, and regular exercises were held as demonstrations or as experiments to improve the techniques and teaching of the Establishment. From 1833 bridging skills were demonstrated annually by the building of a pontoon bridge across the Medway which was tested by the infantry of the garrison and the cavalry from Maidstone. These demonstrations had become a popular spectacle for the local people by 1843, when 43,000 came to watch a field day laid on to test a method of assaulting earthworks for a report to the Inspector General of Fortifications. In 1869 the title of the Royal Engineers Establishment was changed to "The School of Military Engineering" (SME) as evidence of its status, not only as the font of engineer doctrine and training for the British Army, but also as the leading scientific military school in Europe.

A Bailey bridge being deployed in the Korean War to replace a bridge destroyed in combat.

The dawn of the internal combustion engine marked the beginning of a significant change in military engineering. With the arrival of the automobile at the end of the 19th century and heavier than air flight at the start of the 20th century, military engineers assumed a major new role in supporting the movement and deployment of these systems in war. Military engineers gained vast knowledge and experience in explosives. They were tasked with planting bombs, landmines and dynamite.

At the end of World War I, the standoff on the Western Front caused the Imperial German Army to gather experienced and particularly skilled soldiers to form "Assault Teams" which would break through the Allied trenches. With enhanced training and special weapons (such as flamethrowers), these squads achieved some success, but too late to change the outcome of the war. In early WWII, however, the Wehrmacht "Pioniere" battalions proved their efficiency in both attack and defense, somewhat inspiring other armies to develop their own combat engineers battalions. Notably, the attack on Fort Eben-Emael in Belgium was conducted by Luftwaffe glider-deployed combat engineers.

The need to defeat the German defensive positions of the "Atlantic wall" as part of the amphibious landings in Normandy in 1944 led to the development of specialist combat engineer vehicles. These, collectively known as Hobart's Funnies, included a specific vehicle to carry combat engineers, the Churchill AVRE. These and other dedicated assault vehicles were organised into the specialised 79th Armoured Division and deployed during Operation Overlord – 'D-Day'.

Other significant military engineering projects of World War II include Mulberry harbour and Operation Pluto.

Modern military engineering still retains the Roman role of building field fortifications, road paving and breaching terrain obstacles. A notable military engineering task was, for example, breaching the Suez Canal during the Yom Kippur War.

Education

Military engineers can come from a variety of engineering programs. They may be graduates of mechanical, electrical, civil, or industrial engineering.

Sub-discipline

Modern military engineering can be divided into three main tasks or fields: combat engineering, strategic support, and ancillary support. Combat engineering is associated with engineering on the battlefield. Combat engineers are responsible for increasing mobility on the front lines of war such as digging trenches and building temporary facilities in war zones. Strategic support is associated with providing service in communication zones such as the construction of airfields and the improvement and upgrade of ports, roads and railways communication. Ancillary support includes provision and distribution of maps as well as the disposal of unexploded warheads. Military engineers construct bases, airfields, roads, bridges, ports, and hospitals. During peacetime before modern warfare, military engineers took the role of civil engineers by participating in the construction of civil-works projects. Nowadays, military engineers are almost entirely engaged in war logistics and preparedness.

Explosives engineering

Explosives are defined as any system that produces rapidly expanding gases in a given volume in a short duration. Specific military engineering occupations also extend to the field of explosives and demolitions and their usage on the battlefield. Explosive devices have been used on the battlefield for several centuries, in numerous operations from combat to area clearance. Earliest known development of explosives can be traced back to 10th-century China where the Chinese are credited with engineering the world's first known explosive, black powder. Initially developed for recreational purposes, black powder later was utilized for military application in bombs and projectile propulsion in firearms. Engineers in the military who specialize in this field formulate and design many explosive devices to use in varying operating conditions. Such explosive compounds range from black powder to modern plastic explosives. This particular is commonly listed under the role of combat engineers who demolitions expertise also includes mine and IED detection and disposal. For more information, see Bomb disposal.

Military engineering by country

Military engineers are key in all armed forces of the world, and invariably found either closely integrated into the force structure, or even into the combat units of the national troops.

Slovak AM 50 laying a bridge over the Torysa river

Brazil

Brazilian Army engineers can be part of the Quadro de Engenheiros Militares, with its members trained or professionalized by the traditional Instituto Militar de Engenharia (IME) (Military Institute of Engineering), or the Arma de Engenharia, with its members trained by the Academia Militar das Agulhas Negras (AMAN) (Agulhas Negras Military Academy).

In the Brazil's Navy, engineers can occupy the Corpo de Engenheiros da Marinha, the Quadro Complementar de Oficiais da Armada and the Quadro Complementar de Oficiais Fuzileiros Navais. Officers can come from the Centro de Instrução Almirante Wandenkolk (CIAW) (Admiral Wandenkolk Instruction Center) and the Escola Naval (EN) (Naval School) which, through internal selection of the Navy, finish their graduation at the Universidade de São Paulo (USP) (University of São Paulo).

The Quadro de Oficias Engenheiros of the Brazilian Air Force is occupied by engineers professionalized by Centro de Instrução e Adaptação da Aeronáutica (CIAAR) (Air Force Instruction and Adaptation Center) and trained, or specialized, by Instituto Tecnológico de Aeronáutica (ITA) (Aeronautics Institute of Technology).

Russia

•  Russian Empire – Pososhniye lyudi
•  Soviet Union – Engineer Troops (Soviet Union); Assault Engineering Brigades
•  Russia – Russian Engineer Troops

United Kingdom

The Royal School of Military Engineering is the main training establishment for the British Army's Royal Engineers. The RSME also provides training for the Royal Navy, Royal Air Force, other Arms and Services of the British Army, Other Government Departments, and Foreign and Commonwealth countries as required. These skills provide vital components in the Army's operational capability, and Royal Engineers are currently deployed in Afghanistan, Iraq, Cyprus, Bosnia, Kosovo, Kenya, Brunei, Falklands, Belize, Germany and Northern Ireland. Royal Engineers also take part in exercises in Saudi Arabia, Kuwait, Italy, Egypt, Jordan, Canada, Poland and the United States.

United States

Main article: Military engineering of the United States

The prevalence of military engineering in the United States dates back to the American Revolutionary War when engineers would carry out tasks in the U.S. Army. During the war, they would map terrain to and build fortifications to protect troops from opposing forces. The first military engineering organization in the United States was the Army Corps of Engineers. Engineers were responsible for protecting military troops whether using fortifications or designing new technology and weaponry throughout the United States' history of warfare. The Army originally claimed engineers exclusively, but as the U.S. military branches expanded to the sea and sky, the need for military engineering sects in all branches increased. As each branch of the United States military expanded, technology adapted to fit their respective needs.

• United States Army Corps of Engineers
• Air Force Civil Engineer Support Agency, Rapid Engineer Deployable Heavy Operational Repair Squadron Engineers (RED HORSE), and Prime Base Engineer Emergency Force (Prime BEEF)
• The United States Navy Construction Battalion Corps (better known as the Seabees) and Civil Engineer Corps
• United States Marine Corps Combat Engineer Battalions

Other nations

• Department of the Engineer Troops of the Armed Forces of Armenia
• Royal Australian Engineers and the Royal Australian Air Force Airfield Engineers
• Corps of Engineers and Military Engineer Services (MES), Bangladesh Army
• Canadian Military Engineers
• The Danish military engineering corps is almost entirely organized into one regiment, simply named "Ingeniørregimentet" ("The Engineering Regiment").
• Pioniertruppe (Bundeswehr) [de]
• Engineering Arm, including the Paris Fire Brigade
• Indian Army Corps of Engineers
• Indonesian Army Corps of Engineers
• Irish Army Engineer Corps
• Combat Engineering Corps of the Israel Defense Forces
• Engineer Regiment (Namibia)
• Corps of Royal New Zealand Engineers
• Ingeniørbataljonen ("The Engineer Battalion")
• Rejimen Askar Jurutera DiRaja ("Royal Engineer Regiment")
• Pakistan Army Corps of Engineers and the Military Engineering Service
• 10th Engineer Brigade
• South African Army Engineer Formation
• Sri Lanka Engineers and the Engineer Services Regiment
• The Le Quy Don Technical University is the main training establishment for the Vietnamese Army's Corps of Engineers

Catapult

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Catapult

Basic diagram of an Onager, a type of catapult

A catapult is a ballistic device used to launch a projectile a great distance without the aid of gunpowder or other propellants – particularly various types of ancient and medieval siege engines. A catapult uses the sudden release of stored potential energy to propel its payload. Most convert tension or torsion energy that was more slowly and manually built up within the device before release, via springs, bows, twisted rope, elastic, or any of numerous other materials and mechanisms.

In use since ancient times, the catapult has proven to be one of the most persistently effective mechanisms in warfare. In modern times the term can apply to devices ranging from a simple hand-held implement (also called a "slingshot") to a mechanism for launching aircraft from a ship.

The earliest catapults date to at least the 7th century BC, with King Uzziah, of Judah, recorded as equipping the walls of Jerusalem with machines that shot "great stones". Catapults are mentioned in Yajurveda under the name "Jyah" in chapter 30, verse 7. In the 5th century BC the mangonel appeared in ancient China, a type of traction trebuchet and catapult. Early uses were also attributed to Ajatashatru of Magadha in his, 5th century BC, war against the Licchavis. Greek catapults were invented in the early 4th century BC, being attested by Diodorus Siculus as part of the equipment of a Greek army in 399 BC, and subsequently used at the siege of Motya in 397 BC.

Etymology

The word 'catapult' comes from the Latin 'catapulta', which in turn comes from the Greek Ancient Greek: καταπέλτης (katapeltēs), itself from κατά (kata), "downwards" and πάλλω (pallō), "to toss, to hurl". Catapults were invented by the ancient Greeks and in ancient India where they were used by the Magadhan Emperor Ajatashatru around the early to mid 5th century BC.

Greek and Roman catapults

Main article: Greek and Roman artillery

Ancient mechanical artillery: Catapults (standing), the chain drive of Polybolos (bottom center), Gastraphetes (on wall)

Engraving illustrating a Roman catapult design, 1581

Roman "catapult-nest" in the Trajan's Dacian Wars

The catapult and crossbow in Greece are closely intertwined. Primitive catapults were essentially "the product of relatively straightforward attempts to increase the range and penetrating power of missiles by strengthening the bow which propelled them". The historian Diodorus Siculus (fl. 1st century BC), described the invention of a mechanical arrow-firing catapult (katapeltikon) by a Greek task force in 399 BC. The weapon was soon after employed against Motya (397 BC), a key Carthaginian stronghold in Sicily. Diodorus is assumed to have drawn his description from the highly rated history of Philistus, a contemporary of the events then. The introduction of crossbows however, can be dated further back: according to the inventor Hero of Alexandria (fl. 1st century AD), who referred to the now lost works of the 3rd-century BC engineer Ctesibius, this weapon was inspired by an earlier foot-held crossbow, called the gastraphetes, which could store more energy than the Greek bows. A detailed description of the gastraphetes, or the "belly-bow", along with a watercolor drawing, is found in Heron's technical treatise Belopoeica.

A third Greek author, Biton (fl. 2nd century BC), whose reliability has been positively reevaluated by recent scholarship, described two advanced forms of the gastraphetes, which he credits to Zopyros, an engineer from southern Italy. Zopyrus has been plausibly equated with a Pythagorean of that name who seems to have flourished in the late 5th century BC. He probably designed his bow-machines on the occasion of the sieges of Cumae and Milet between 421 BC and 401 BC. The bows of these machines already featured a winched pull back system and could apparently throw two missiles at once.

Philo of Byzantium provides probably the most detailed account on the establishment of a theory of belopoietics (belos = "projectile"; poietike = "(art) of making") circa 200 BC. The central principle to this theory was that "all parts of a catapult, including the weight or length of the projectile, were proportional to the size of the torsion springs". This kind of innovation is indicative of the increasing rate at which geometry and physics were being assimilated into military enterprises.

From the mid-4th century BC onwards, evidence of the Greek use of arrow-shooting machines becomes more dense and varied: arrow firing machines (katapaltai) are briefly mentioned by Aeneas Tacticus in his treatise on siegecraft written around 350 BC. An extant inscription from the Athenian arsenal, dated between 338 and 326 BC, lists a number of stored catapults with shooting bolts of varying size and springs of sinews. The later entry is particularly noteworthy as it constitutes the first clear evidence for the switch to torsion catapults, which are more powerful than the more-flexible crossbows and which came to dominate Greek and Roman artillery design thereafter. This move to torsion springs was likely spurred by the engineers of Philip II of Macedonia. Another Athenian inventory from 330 to 329 BC includes catapult bolts with heads and flights. As the use of catapults became more commonplace, so did the training required to operate them. Many Greek children were instructed in catapult usage, as evidenced by "a 3rd Century B.C. inscription from the island of Ceos in the Cyclades [regulating] catapult shooting competitions for the young". Arrow firing machines in action are reported from Philip II's siege of Perinth (Thrace) in 340 BC. At the same time, Greek fortifications began to feature high towers with shuttered windows in the top, which could have been used to house anti-personnel arrow shooters, as in Aigosthena. Projectiles included both arrows and (later) stones that were sometimes lit on fire. Onomarchus of Phocis first used catapults on the battlefield against Philip II of Macedon. Philip's son, Alexander the Great, was the next commander in recorded history to make such use of catapults on the battlefield as well as to use them during sieges.

The Romans started to use catapults as arms for their wars against Syracuse, Macedon, Sparta and Aetolia (3rd and 2nd centuries BC). The Roman machine known as an arcuballista was similar to a large crossbow. Later the Romans used ballista catapults on their warships.

Other ancient catapults

In chronological order:

• 19th century BC, Egypt, walls of the fortress of Buhen appear to contain platforms for siege weapons.
• c.750 BC, Judah, King Uzziah is documented as having overseen the construction of machines to "shoot great stones".
• between 484 and 468 BC, India, Ajatashatru is recorded in Jaina texts as having used catapults in his campaign against the Licchavis.
• between 500 and 300 BC, China, recorded use of mangonels. They were probably used by the Mohists as early as the 4th century BC, descriptions of which can be found in the Mojing (compiled in the 4th century BC). In Chapter 14 of the Mojing, the mangonel is described hurling hollowed out logs filled with burning charcoal at enemy troops. The mangonel was carried westward by the Avars and appeared next in the eastern Mediterranean by the late 6th century AD, where it replaced torsion powered siege engines such as the ballista and onager due to its simpler design and faster rate of fire. The Byzantines adopted the mangonel possibly as early as 587, the Persians in the early 7th century, and the Arabs in the second half of the 7th century. The Franks and Saxons adopted the weapon in the 8th century.

Medieval catapults

Replica of a Petraria Arcatinus

Petraria Arcatinus catapult in Mercato San Severino, Italy

Catapult 1 Mercato San Severino

Castles and fortified walled cities were common during this period and catapults were used as siege weapons against them. As well as their use in attempts to breach walls, incendiary missiles, or diseased carcasses or garbage could be catapulted over the walls.

Defensive techniques in the Middle Ages progressed to a point that rendered catapults largely ineffective. The Viking siege of Paris (885–6 A.D.) "saw the employment by both sides of virtually every instrument of siege craft known to the classical world, including a variety of catapults", to little effect, resulting in failure.

The most widely used catapults throughout the Middle Ages were as follows:

Ballista

Ballistae were similar to giant crossbows and were designed to work through torsion. The projectiles were large arrows or darts made from wood with an iron tip. These arrows were then shot "along a flat trajectory" at a target. Ballistae were accurate, but lacked firepower compared with that of a mangonel or trebuchet. Because of their immobility, most ballistae were constructed on site following a siege assessment by the commanding military officer.

Springald

The springald's design resembles that of the ballista, being a crossbow powered by tension. The springald's frame was more compact, allowing for use inside tighter confines, such as the inside of a castle or tower, but compromising its power.

Mangonel

This machine was designed to throw heavy projectiles from a "bowl-shaped bucket at the end of its arm". Mangonels were mostly used for “firing various missiles at fortresses, castles, and cities,” with a range of up to 1,300 ft (400 m). These missiles included anything from stones to excrement to rotting carcasses. Mangonels were relatively simple to construct, and eventually wheels were added to increase mobility.

Onager

Mangonels are also sometimes referred to as Onagers. Onager catapults initially launched projectiles from a sling, which was later changed to a "bowl-shaped bucket". The word Onager is derived from the Greek word onagros for "wild ass", referring to the "kicking motion and force" that were recreated in the Mangonel's design. Historical records regarding onagers are scarce. The most detailed account of Mangonel use is from “Eric Marsden's translation of a text written by Ammianus Marcellius in the 4th Century AD” describing its construction and combat usage.

Trebuchet

Mongol warriors using trebuchet to besiege a city

Trebuchets were probably the most powerful catapult employed in the Middle Ages. The most commonly used ammunition were stones, but "darts and sharp wooden poles" could be substituted if necessary. The most effective kind of ammunition though involved fire, such as "firebrands, and deadly Greek Fire". Trebuchets came in two different designs: Traction, which were powered by people, or Counterpoise, where the people were replaced with "a weight on the short end". The most famous historical account of trebuchet use dates back to the siege of Stirling Castle in 1304, when the army of Edward I constructed a giant trebuchet known as Warwolf, which then proceeded to "level a section of [castle] wall, successfully concluding the siege".

Couillard

A simplified trebuchet, where the trebuchet's single counterweight is split, swinging on either side of a central support post.

Leonardo da Vinci's catapult

Leonardo da Vinci sought to improve the efficiency and range of earlier designs. His design incorporated a large wooden leaf spring as an accumulator to power the catapult. Both ends of the bow are connected by a rope, similar to the design of a bow and arrow. The leaf spring was not used to pull the catapult armature directly, rather the rope was wound around a drum. The catapult armature was attached to this drum which would be turned until enough potential energy was stored in the deformation of the spring. The drum would then be disengaged from the winding mechanism, and the catapult arm would snap around. Though no records exist of this design being built during Leonardo's lifetime, contemporary enthusiasts have reconstructed it.

Modern use

Military

French troops using a catapult to throw hand grenades and other explosives during World War I

The last large scale military use of catapults was during the trench warfare of World War I. During the early stages of the war, catapults were used to throw hand grenades across no man's land into enemy trenches. They were eventually replaced by small mortars.

The SPBG (Silent Projector of Bottles and Grenades) was a soviet proposal anti-tank weapon that launched grenades from a spring loaded shuttle up to 100 m (330 ft).

In the 1840s, the invention of vulcanized rubber allowed the making of small hand-held catapults, either improvised from Y-shaped sticks or manufactured for sale; both were popular with children and teenagers. These devices were also known as slingshots in the United States.

Special variants called aircraft catapults are used to launch planes from land bases and sea carriers when the takeoff runway is too short for a powered takeoff or simply impractical to extend. Ships also use them to launch torpedoes and deploy bombs against submarines. Small catapults, referred to as "traps", are still widely used to launch clay targets into the air in the sport of clay pigeon shooting.

Entertainment

In the 1990s and early 2000s, a powerful catapult, a trebuchet, was used by thrill-seekers first on private property and in 2001–2002 at Middlemoor Water Park, Somerset, England, to experience being catapulted through the air for 100 feet (30 m). The practice has been discontinued due to a fatality at the Water Park. There had been an injury when the trebuchet was in use on private property. Injury and death occurred when those two participants failed to land onto the safety net. The operators of the trebuchet were tried, but found not guilty of manslaughter, though the jury noted that the fatality might have been avoided had the operators "imposed stricter safety measures." Human cannonball circus acts use a catapult launch mechanism, rather than gunpowder, and are risky ventures for the human cannonballs.

Early launched roller coasters used a catapult system powered by a diesel engine or a dropped weight to acquire their momentum, such as Shuttle Loop installations between 1977 and 1978. The catapult system for roller coasters has been replaced by flywheels and later linear motors.

Pumpkin chunking is another widely popularized use, in which people compete to see who can launch a pumpkin the farthest by mechanical means (although the world record is held by a pneumatic air cannon).

Other

In January 2011, a homemade catapult was discovered that was used to smuggle cannabis into the United States from Mexico. The machine was found 20 ft (6.1 m) from the border fence with 4.4 pounds (2.0 kg) bales of cannabis ready to launch.