A laser-guided bomb (LGB) is a guided bomb that uses semi-active laser guidance to strike a designated target with greater accuracy than an unguided bomb. First developed by the United States during the Vietnam War, laser-guided bombs quickly proved their value in precision strikes of difficult point targets. These weapons use on-board electronics to track targets that are designated by laser, typically in the infrared spectrum, and adjust their glide path to precisely strike the target. Since the weapon is tracking a light signature, not the object itself, the target must be illuminated from a separate source, either by ground forces, by a pod on the attacking aircraft, or by a separate support aircraft.
Data from Vietnam showed that laser-guided bombs achieved direct hits nearly 50% of the time, versus just 5.5% for unguided bombs. Because of this dramatically higher precision, laser-guided munitions can carry less explosive and cause less collateral damage than unguided munitions. Today, laser-guided bombs are one of the most common and widespread guided bombs, used by a large number of the world's air forces.
Laser-guided weapons were first developed in the United States and United Kingdom in the early 1960s. The United States Air Force issued the first development contracts in 1964, leading to the development of the Paveway series, which was used operationally in Vietnam starting in 1968. Although there were a variety of technical and operational problems, the results were generally positive. LGBs proved to offer a much higher degree of accuracy than unguided weapons, but without the expense, complexity, and limitations of guided air-to-ground missiles like the AGM-12 Bullpup. The LGB proved particularly effective against difficult fixed targets like bridges, which previously had required huge loads of "dumb" ordnance to destroy.
It was determined that 48% of Paveways dropped during 1972–73 around Hanoi and Haiphong achieved direct hits, compared with only 5.5% of unguided bombs dropped on the same area a few years earlier. The average Paveway landed within 23 feet of its target, as opposed to 447 feet for gravity bombs. The leap in accuracy brought about primarily by laser guidance made it possible to take out heavily defended, point objectives that had eluded earlier air raids.