The Vietnam War was the first major conflict in which guided weapons were deployed in large numbers by both sides. This wasn't true from the start, though. When the United States began the bombing campaign against North Vietnam in 1965, the weapons it employed were simple free-fall bombs similar to those used in the Second World War. The Vietnamese air defenses consisted of airborne and ground-based guns of a similar vintage. As the conflict progressed, however, both sides fielded superior new weapons in the form of missiles and guided bombs.

Air-to-Air Missiles

Probably the best-known air-to-air missile of the Vietnam era was the AIM-9 Sidewinder, which was used extensively by both the U.S. Air Force and the U.S. Navy. Commonly referred to as a "heat-seeking" missile, the Sidewinder used an infrared sensor for guidance. The most advanced fighter of the Vietnam War, the F-4 Phantom, was also equipped with a longer range, radar-guided missile called the AIM-7 Sparrow. North Vietnamese aircraft used a Soviet heat-seeking missile known in the West as the AA-2 Atoll, which was similar in design to the Sidewinder and may even have been a direct copy of it.

Surface-to-Air Missiles

The most potent threat faced by American aircraft flying over North Vietnam was the Soviet-built SA-2 surface-to-air missile, or SAM. Conventional ground-based anti-aircraft artillery is limited to relatively low-flying targets, but this was not the case with the SA-2. The missile was effective to an altitude of 20 miles, and could travel at 3.5 times the speed of sound. SAMs were deployed by the North Vietnamese around key target areas, causing enormous problems for the U.S. planners. They either had to choose routes that avoided known SAM sites, or take steps to destroy the SAMs before they left the ground.

Wild Weasels

To deal with the SAM threat, the U.S. Air Force devised a new type of combat mission codenamed "Wild Weasel," which was specifically targeted at ground-based air defenses. A special type of weapon was developed for this purpose. Called the AGM-45 Shrike, this was similar to the Sparrow radar-guided missile, except that the signal it was designed to home in on was the one coming from the enemy SAM radar. Later in the war, a more sophisticated weapon called the AGM-78 Standard ARM -- Anti-Radiation Missile -- became the mainstay of Wild Weasel operations.

Guided Bombs

Most of the ordnance dropped on North Vietnam consisted of unguided "dumb" bombs. However, the later years of the campaign saw the gradual introduction of more sophisticated "smart" weapons. The first of these was the AGM-62 Walleye glide bomb, which guided itself toward the designated target by means of a TV camera in its nose. Even more precise targeting could be achieved using the Paveway family of laser-guided bombs, or LGBs, which saw their first operational use in Vietnam. Two aircraft are involved in an LGB engagement -- the first to direct a laser beam at the target and the second to drop the bomb, which then follows the laser beam to the target.