smart weapon, missile or steerable bomb equipped with a laser, television, or satellite guidance system. Smart weapons, which use guidance systems that rely on external assistance, are distinguished from brilliant weapons, which are totally self-guided. In the case of a smart bomb with a laser guidance system, an aircraft pilot aims a laser beam at the target, a computer keeps the beam locked on the target, and the bomb has a sensor programmed to find the reflection of the laser's light. A guidance computer adjusts the path of the bomb after it is released, using movable fins to steer. A television guidance system uses a television camera in the nose of the weapon to lock onto the image of the target identified by the pilot. Satellite-guided bombs have guidance computers that use signals from navigation satellites to confirm that they are on target; the tail fins are adjusted to control the bomb's course as it falls. Cruise missiles also utilize information from navigation satellites to maintain a proper course during flight. Extensions of smart-weapon technology are off-road mines that can "listen" for moving vehicles and attack them, "thinking" antipersonnel mines that are activated or deactivated automatically after a set period of time, and missile and artillery fire targeted by space-based intelligence-gathering satellites.

radiological weapon: see radiation weapon.

radiation weapon or radiological weapon, a bomb or warhead that uses conventional chemical explosives to disperse radioactive material, sometimes called a "dirty bomb." Designed to produce radiation sickness in a military force or a civilian population instead of destroy a target, radiation weapons typically consist of a highly radioactive material encased in lead and surrounded by a high explosive. During the 1980s, Iraq developed and tested a radiation weapon that was intended to produce health effects that would be difficult to explain, but decided to abandoned the project because a radiation level low enough to escape detection was also insufficient to cause significant medical problems in the weeks following an attack. See also nuclear weapons.

Weapon with the capacity to inflict death and destruction indiscriminately and on a massive scale. The term has been in currency since at least 1937, when it was used to describe massed formations of bomber aircraft. Today WMDs are nuclear, biological, or chemical weapons—frequently referred to collectively as NBC weapons. Efforts to control the spread of WMDs are enshrined in international agreements such as the Nuclear Non-proliferation Treaty of 1968, the Biological Weapons Convention of 1972, and the Chemical Weapons Convention of 1993. See nuclear weapon; chemical warfare; biological warfare.

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or atomic weapon or thermonuclear weapon

Bomb or other warhead that derives its force from nuclear fission, nuclear fusion, or both and is delivered by an aircraft, missile, or other system. Fission weapons, commonly known as atomic bombs, release energy by splitting the nuclei of uranium or plutonium atoms; fusion weapons, known as hydrogen bombs or thermonuclear bombs, fuse nuclei of the hydrogen isotopes tritium or deuterium. Most nuclear weapons actually combine both processes. Nuclear weapons are the most potent explosive devices ever invented. Their destructive effects include not only a blast equivalent to thousands of tons of TNT but also blinding light, searing heat, and lethal radioactive fallout. The number of nuclear weapons reached a peak of some 32,000 for the United States in 1966 and some 33,000 for the Soviet Union in 1988. Since the end of the Cold War, both countries have decommissioned or dismantled thousands of warheads. Other declared nuclear powers are the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is widely assumed to possess nuclear weapons. Some countries, such as South Africa, Brazil, Argentina, and Iraq, have acknowledged pursuing nuclear weapons in the past but have abandoned their programs. Seealso Nuclear Non-proliferation Treaty; Nuclear Test-Ban Treaty.

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Use of lethal or incapacitating chemical weapons in war, and the methods of combating such agents. Chemical weapons include choking agents such as the chlorine and phosgene gas employed first by the Germans and later by the Allies in World War I; blood agents such as hydrogen cyanide or cyanogen gas, which block red blood cells from taking up oxygen; blister agents such as sulfur gas and Lewisite, also dispensed as a gas, which burn and blister the skin; and nerve agents such as Tabun, Sarin, Soman, and VX, which block the transmission of nerve impulses to the muscles, heart, and diaphragm. The horrific casualties suffered in World War I led to the 1925 Geneva Protocol, which made it illegal to employ chemical weapons but did not ban their production. Chemical weapons were used a number of times afterward, most notably by Italy in Ethiopia (1935–36), by Japan in China (1938–42), by Egypt in Yemen (1966–67), and by Iran and Iraq against each other (1984–88). During the Cold War the Soviet Union and U.S. built up enormous chemical arsenals; these were dismantled under the terms of the 1993 Chemical Weapons Convention, which prohibits all development, production, acquisition, stockpiling, or transfer of such weapons. Not all countries have signed the convention, and many are suspected of pursuing clandestine chemical programs. Many military forces have adopted various defensive measures, including chemical sensors, protective garments and gas masks, decontaminants, and injectable antidotes, and some have reserved the option of retaliating in kind to any chemical attack. In 1995 a religious cult killed 12 civilians and injured thousands more with Sarin gas in Tokyo; this pointed out the power of chemical agents as weapons of terror as well as the difficulty of protecting civilian populations. Seealso biological warfare.

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or germ warfare

Military use of disease-producing or poisonous agents, and the means for defending against such agents. Biological warfare agents include many bacteria, such as those which cause anthrax, brucellosis, and typhus; viruses that cause diseases such as equine encephalitis; fungi such as rice blast, cereal rust, wheat smut, and potato blight; and toxins such as botulinum and ricin that are extracted from living organisms. Biological warfare dates from ancient times when warring groups would try to poison enemy soldiers with rotting or diseased corpses, infect cattle and horses, or spread contagion through civilian populations. Following the horrors of World War I, a 1925 Geneva Protocol prohibited the use of biological agents in warfare; however, this did not prevent Japan from using them in China during World War II. During the Cold War the Soviet Union as well as the U.S. and its allies built huge stockpiles of biological agents. Both sides signed the 1972 Biological Weapons Convention, which prohibits the production, stockpiling, or development of biological weapons and requires the destruction of existing stockpiles, but the Soviets conducted a clandestine program until the 1990s. Biological weapons programs can be concealed easily, and the 1972 convention contains no provisions for inspection and reporting. As a result, many states have been suspected of developing biological warfare agents, and some modern armed forces have prepared defensive measures. These include battlefield sensors, protective garments and masks, sterilizing agents, and vaccines.

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Any of several guns, missiles, and mines intended for use against tanks. Land mines, ordinary artillery, and other projectiles were used to destroy tanks in World War I. By World War II antitank guns had been developed; they frequently fired special ammunition such as the hollow charge shell, which exploded on impact with great penetrating force. Various antitank missiles and launching devices, including the bazooka, were also used in the war.

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