Other than high explosives, these occur in three principal groups within the military context: propellent explosives such as gunpowder used in firearms; atomic explosives; and explosives formed of a mixture of fuel and air, such as napalm. Preceding all of these was Greek fire, a combustible composition utilizing naphtha and sulphur but not saltpetre; it appears to have been used first in the 7th century ad.
The discovery of saltpetre is of great significance in the history of explosives since it is a principal component of gunpowder. Believed to have been first used by the Chinese in the early 11th century, saltpetre's explosive properties were soon taken up by the Arabs and in India; its use was translated to Europe in the 14th century when both Roger Bacon and St Albertus Magnus gave written recipes for gunpowder. This was the principal propellent explosive in use for military purposes until the mid-19th century, used for both small arms and artillery, as well as in grenades and bursting shells, forming both the main charge and the igniting charge in flintlock small arms. Gunpowder is a mixture of saltpetre, charcoal, and sulphur, and early gunpowder was just that: a powder. It burnt slowly, even in the confined space of a barrel's chamber, and early firearms were underpowdered as a result. The process of ‘corning’ gunpowder was developed during the 15th century; this allowed for the powder to be manufactured in grains of differing sizes. Large-grained or ‘corned’ gunpowder burnt more quickly and powerfully and increased the power of firearms and it was used as the main charge. ‘Mealed’, or smaller-grained, powder was used as the priming charge. Military muskets tended to use corned powder for both main and priming charges.
A fulminate of mercury composition encased in a copper cap replaced gunpowder as the igniting charge in the percussion lock and, as breech-loading firearms began to be developed, so the search for a main charge other than gunpowder, which was both smoky and barrel-fouling, began. Gun cotton was developed and experimented with in the 1840s but proved unstable and over-powerful as a propellant. By the end of the 19th century, gunpowder had been replaced as the principal propellent explosive in small arms by the smokeless powder known as cordite—a nitrocellulose and nitroglycerine compound with acetone as a dissolving agent. After WW I explosive propellants became refined into compounds of nitrodiglycol and nitrocellulose which caused less wear on the bores of rifle and artillery barrels. Flashless propellent explosive was achieved by adding nitroguanidine to the existing nitro-compound and this triple combination continues in use, in varying mixtures, especially for armour-piercing ammunition which requires the generation of very high muzzle velocities.
Atomic explosives were a war-led product of research into atomic fission, which was being investigated in a number of research institutes in the 1930s. Developed under the auspices of the Manhattan Project in top secret conditions in the USA by 1945, atomic explosives were first tested in the New Mexico desert and then used at Hiroshima and Nagasaki, claiming nearly 200, 000 lives. The atomic bomb was superseded in the 1950s by the hydrogen bomb, the potential power of which was at least ten times that of its predecessor. Atomic or nuclear bombs were refined into warheads for surface, submarine, or air-launched missiles and a distinction formed between strategic nuclear weapons and tactical ones. Strategic targets involve the use of large devices in order to create massive and condign destruction; tactical ones would be attacked by smaller devices with effects limited to an immediate and defined area.
Fuel-air explosives are a sophistication of high explosive and were developed during WW I to produce incendiary bombs and flame-thrower fuel. Unlike true high explosive, which concentrates its destructive power at one point, fuel-air explosive produces a widespread and even blast wave, suitable for clearing minefields or destroying soft targets over a large area from point of impact. Constructed from chemical mixtures such as petrol, sodium nitrate, and powdered magnesium, the best known fuel-air explosive is probably napalm, which was first used during WW II but had widespread use during the Vietnam war.
Bibliography
- Bailey, A., and Murray, S. G., Explosives, Propellants and Pyrotechnics (London, 1989).
- Freedman, Lawrence, The Evolution of Military Strategy (London, 1981).
- Moss, Norman, The Men who Play God: The Story of the Hydrogen Bomb (London, 1970).
- Partington, James R., A History of Greek Fire and Gunpowder (Cambridge, 1960)
— Stephen Wood
