Burning Tar

Early thermal weapons, which used heat or burning action to destroy or damage enemy personnel, fortifications or territories, were employed in warfare during the classical and medieval periods (approximately the 8th century BC until the mid-16th century AD).

Incendiary devices were frequently used as projectiles during warfare, particularly during sieges and naval battles: some substances were boiled or heated to inflict damage by scalding or burning; other substances relied on their chemical properties to inflict burns or damage. These weapons or devices could be used by individuals, thrown by siege engines, or utilised as army strategy. Incendiary mixtures, such as the petroleum-based Greek fire, could be launched by throwing machines or administered through a siphon. Sulfur- and oil-soaked materials were sometimes ignited and thrown at the enemy, or attached to spears, arrow and bolts and fired by hand or machine.

The simplest and most common thermal projectiles were boiling water and hot sand, which could be poured over attacking personnel. Other anti-personnel weapons included the use of hot pitch, oil, resin, animal fat and other similar compounds. Smoke was used to confuse or drive off attackers. Substances such as quicklime and sulfur could be toxic and blinding.

Fire and incendiary weapons were also used against enemy structures and territory, sometimes on a massive scale. Large tracts of land, towns and villages were frequently ignited as part of a scorched earth strategy. Some siege techniques—such as mining and boring—relied on combustibles and fire to complete the collapse of walls and structures.

Towards the latter part of the period, gunpowder was invented, which increased the sophistication of the weapons, starting with fire lances, which led to the eventual development of the cannon and other firearms. Development of the early weapons has continued ever since, with modern war weapons such as napalm, flame throwers, and other explosives having direct roots in the original early thermal weapons. Fire-raising and other destructive strategies can still be seen in modern strategic bombing.

"Fire and sword"

The destruction of enemy possessions and territory was a fundamental strategy of war, serving the dual purpose of punishment and deprivation of resources.Prestwich, pp. 198–200 Until the 5th century BC, the Greeks had little expertise in siege warfare and relied on a strategy of devastation to draw the enemy out; they destroyed crops, trees and houses. Centuries later, the Byzantines recommended this strategy, even though they had developed siege technology.

Fire was the easiest way of harrying and destroying territories, and could be done easily and quickly by small forces.Traquir, p. 198 It was a strategy put to good use by the Scots during the Wars of Independence; they repeatedly launched raids into northern England, burning much of the countryside until the whole region was transformed. King Edward II of England pursued one raiding party in 1327 by following the lights of burning villages.

The tactics were replicated by England during the Hundred Years' War; fire became their chief weapon as they laid waste to the French countryside during lightning raids called chevauchées, in a form of economic warfare. One estimate records the destruction of over 2000 villages and castles during one raid in 1339.

As well as causing the destruction of lands, food and belongings, fire could also be used to divert manpower. 13th century Mongol armies regularly sent out small detachments from their main forces to start grass fires and fire settlements as diversions.

Devastation by fire was not only used as an offensive tactic; some countries and armies employed "scorched earth" policies on their own land to deprive invading armies of all food and forage. Robert I of Scotland reacted to the English invasion of 1322 by launching punitive and diversionary chevauchées into north-west England, then retreating to Culross, burning as he went the Scottish lands which lay in the path of the English army. The English ran out of food and had to abandon the campaign.

Such acts of aggression were not limited to wars against territorial enemies, but could form part of the strategies of conquest, subjugation and punishment of rebellion. Alexander the Great suppressed a revolt in Thebes, Greece in 335 BC, after which he ordered the city to be torched and laid waste. Alexander ordered (or allowed) a similar arson at Persepolis in 330 BC. It was a policy which was repeated throughout the period. William I of England, following his conquest of England in the 11th century, asserted his control of Northumbria by destructive campaigns throughout the region: "He ordered that crops and herds, tools and food should be burned to ashes. More than 100,000 people perished of hunger", reported Orderic Vitalis, a contemporary chronicler. It was a scene repeated the following century, during the anarchy of Stephen of England's reign. Civil war erupted between Stephen's supporters and those of the Empress Matilda, a rival claimant for the throne. The ''Gesta Stephani'' tells of the deeds of one of Stephen's supporters, Philip of Gloucester, by describing how he "raged in all directions with fire and sword, violence and plunder", reducing territory to "bare fields and dreadful desert".

Techniques of use

At the simplest level, fire itself was used as a weapon to cause large-scale destruction, or to target specific enemy positions or machinery. It was frequently used against siege engines and wooden structures.Nossov, p. 190 Incendiary weapons could be used to set fire to towns and fortifications, and a wide range of thermal weapons were used against enemy personnel. Some armies developed specialised "fire-troops". By 837, many Muslim armies had groups of "naffatin" (fire archers),Nicolle (1996), p. 85 and when the Mamluk Sultanate raised a fleet for an attack on Cyprus they had "nafata", or firetroops.Nicolle (1996), p. 181

Simple fire-raising

The burning of enemy positions and equipment was not necessarily a complicated procedure, and many fires were set by individuals using common materials. When William of Normandy's army besieged Mayenne in 1063, they shot fire into the castle to panic the garrison, while two boys stole into the castle in order to start a fire within. The garrison surrendered.Bradbury (2004), p. 151

Besieged forces would sometimes launch sorties in an attempt to fire the attackers' camps or equipment. When Hugh Capet besieged Laon in 986–987, his troops became drunk one night, and Duke Charles's men sallied forth and torched the camp, forcing Hugh to abandon the siege.Bradbury (2004), p. 202

The besieged were not the only ones who might fire siege equipment; when Frederick I Barbarossa abandoned his siege of Alessandria in 1175, he burned his own camp and equipment.

However, like all weapons, fire-raising had its own dangers. In 651 Penda of Mercia attempted to win Bamburgh Castle by building a pyre at its base from planks, beams, wattle and thatch. The wind changed direction and the fire blew back on Penda's men, who had to abandon the attack. This fortuitous wind-change was credited to Saint Aidan, who saw the smoke from the Farne Islands and prayed for the defenders.Bradbury (2004), p. 135

Throwing machines

Various throwing machines were in use throughout the classical and medieval periods. Generally referred to as "artillery", these engines could hurl, fire or shoot missiles and most could be used or adapted for throwing thermal weapons, by attacking and defending forces.Bradbury (2004), p. 299 Barrels, fire pots and other breakable containers of pitch, Greek fire, and other incendiary mixtures could be thrown;Nicolle (1995), p. 208 other machines fired arrows and bolts, which could be ignited, or adapted to carry flammable mixtures.Nossov, pp. 133–5 From the 12th century, Muslims in Syria were using clay and glass grenades for fire weapons, thrown by machines.

Most of the terms used for throwing machines were vague, and could refer to different engines, all of which went through changes and developments over the period. Among the most common were the ballista, mangonel and trebuchet. The ballista was similar in form to a crossbow, though much larger, and used a string-winding mechanism to fire a missile or bolt placed in a groove.Bradbury (2004), p. 300 Other giant crossbows were used throughout the period, and an "espringal", based on the ballista, which threw large bolts, was developed in the 13th century. Torsion-powered arrow firers had been used from 400 BC, and were adapted for stones. A mangonel had a wooden spoon-shaped arm, to hold a stone or other projectile, which was manipulated under tension from a twisted rope.Bradbury (2004), p. 305 The trebuchet was an advanced development of the 12th or 13th century, which used a counter-weight to power the throwing arm, and was the major siege engine until the cannon became widespread.

In mining

Forces attacking a castle or other strong fortification sometimes sought to undermine the foundations by digging "mines" or tunnels underneath them. Usually, such mining or digging machinery was protected by a ''tortoise'' (also called a ''cat'', ''sow'', or ''owl''): a covered shed on wheels, which shielded the miners from missile attack.Nossov, p. 123

As the tunnels were constructed, they were generally supported by wooden beams and posts.Bradbury (2004), p. 303 Once the mine had been finished, the internal space was filled with combustibles, such as brushwood, firewood, resin, and other incendiary substances; once ignited, these would burn the supporting props, causing the mine to collapse, bringing down with it the structures lying above.Nossov, p. 124 From the 15th century, gunpowder was also used, although the aim remained to burn the props.

Defenders might sometimes dig counter-tunnels in order to reach the enemy's mines and launch an attack; frequently thermal weapons were used to drive the besiegers from the tunnels.

Rather than undermining a structure, some besiegers used borers to drill holes in the outer walls in an effort to destroy them; such methods were more effective than rams