bomb

Container filled with explosive or chemical material and generally used in warfare. There are also incendiary bombs and nuclear bombs and missiles (see nuclear warfare). Any object designed to cause damage by explosion can be called a bomb (car bombs, letter bombs). Initially dropped from aeroplanes (from World War I), bombs were in World War II also launched by rocket (V1, V2). The 1960s saw the development of missiles that could be launched from aircraft, land sites, or submarines. In the 1970s laser guidance systems were developed to hit small targets with accuracy.

Aerial bombing started in World War I (1914–18) when the German air force carried out 103 raids on Britain, dropping 269 tonnes of bombs, killing 670 and wounding 1,960. In World War II (1939–45) nearly twice this tonnage was dropped on London in a single night, and at the peak of the Allied air offensive against Germany, more than ten times this tonnage was regularly dropped in successive nights on one target. Raids in which nearly 1,000 heavy bombers participated were frequent. They were delivered either in ‘precision’ or ‘area’ attacks and advances were made in blind bombing, in which the target is located solely by instruments and is not visible through a bombsight. In 1939 bombs were commonly about 115 kg/250 lb and 230 kg/500 lb, but by the end of the war the ten‐tonner was being produced.

The fission or atom bomb was developed in the 1940s and the USA exploded three during World War II: first a test explosion on 16 July 1945, at Alamogordo, New Mexico, USA, then on 6 August the first to be used in actual warfare was dropped over Hiroshima and three days later another over Nagasaki, Japan. The force of the bomb on Hiroshima was equivalent to 12,700 tonnes of TNT, and on Nagasaki, 22,000 tonnes of TNT. The fusion or hydrogen bomb was developed in the 1950s, and by the 1960s intercontinental 100‐megatonne nuclear warheads could be produced (5,000 times more powerful than those of World War II). The USA and former USSR between them possessed stockpiles sufficient to destroy each other's countries and populations several times over (see also nuclear winter). More recent bombs produce less fallout, a ‘dirty’ bomb being one that produces large quantities of radioactive debris from a U‐238 (uranium isotope) casing.

The danger of nuclear weapons increases with the number of nations possessing them (USA 1945, USSR 1949, UK 1952, France 1960, China 1964), and nuclear‐arms verification has been complicated by the ban on above‐ground testing. Testing grounds include Lop Nur (China); Mururoa Atoll in the South Pacific (France); Nevada Desert, Amchitka Islands in the Aleutians (USA); Semipalatinsk (Kazakhstan); and Novaya Zemlya Islands in the Arctic (Russia). Under the Outer Space Treaty 1966 nuclear warheads may not be sent into orbit, but this measure has been circumvented by more sophisticated weapons. The Fractional Orbital Bombardment System (FOBS) sends a warhead into a low partial orbit, followed by a rapid descent to Earth. This renders it both less vulnerable to ballistic missile defence systems and cuts the warning time to three minutes. The rapid development of laser guidance systems in the 1970s meant that precise destruction of small but vital targets could be more effectively achieved with standard 450 kg/1,000 lb high‐explosive bombs. The laser beam may be directed at the target by the army from the ground, or alternatively from high‐performance aircraft accompanying the bombers, for example, the Laser Ranging Marker Target System (LRMTS). These systems' effectiveness was demonstrated during the Gulf War of 1991.