The M72 LAW is a man-portable anti-armor weapon. LAW is an acronym, is pronounced as the word, and stands for 'Light Anti-armor Weapon.' It is an infantry rocket launcher designed in the United States and produced there and in Norway (under license) for use by the United States and allied militaries.
At the end of the Korean War, the primary U.S. infantry anti-armor weapon was still the World War II-era M9A1 Bazooka, a large reloadable rocket launcher familiar to anyone who has watched World War II movies. The problem with the Bazooka was twofold: for one, it was too large, and for another, it was too small. The Bazooka, in its final incarnation, weighed over 14 pounds empty, and was large enough that a joint had been engineered in it to allow it to break down for carrying. Using it required a two-man team - an operater and a spotter/loader, since the tube was long enough (54 inches, or 1.35+ meters) to be impractical to swing vertical for loading. The loader stayed behind the operator, notifying him when the weapon was ready, and kept watch over the pair.
At the same time, the rockets used by the Bazooka, the M6 series rocket, were too small. The warhead on the M6 could, in ideal circumstances, penetrate around 4 inches of steel armor plate, which was sufficient for at least rear and side shots on most tanks available during World War II. After that conflict, however, tanks and armor began evolving rapidly, and the Bazooka was unable to keep up.
In 1956, the U.S. Army began to look for a replacement for the Bazooka. A U.S. contractor proposed a design, and by 1961 the first LAWs were in use. The LAW itself solved both problems of the Bazooka. It was smaller than the M9 series, and more powerful. Probably the most important difference between the LAW and its predecessor is that the M72 is a one-shot launcher; the rocket projectile is prepackaged inside the disposable launch tube, and when the rocket has been fired, the user simply discards the now-useless tube. The M72, loaded with a rocket, weighs 5.1 lbs (around 2.15 kg) and measures under a meter in length (don't you hate it when I mix units?). In addition, it's quite cheap, and can be issued as a single 'all-up' round of ammunition to soldiers, meaning that an organic anti-armor capability can not only be provided to small units, but spread around through them so that it is more readily available.
The warhead on the M72's rocket can penetrate around a foot (0.3 meter) of steel armor plate, or up to 6 feet of loose soil, due to its more advanced HEAT warhead.
The LAW comes as a collapsed tube, sealed to be watertight with the rocket unarmed. It can be easily carried or packed in this configuration. When the launcher is 'opened,' the user slides the rear of the weapon backwards, and an inner tube extends out. This both cocks the firing mechanism and arms the rocket. Doing this breaks the seals, so that the weapon is no longer watertight if it is recollapsed; in addition, early LAWs would not disarm the rocket, merely remove the firing mechanism from ready position when reclosed and thus reclosing them was not advised.
When the launcher opens, a simple optical sight flips up atop the middle of the tube, and a front gate sight flips up at the fore. The user places the tube on their shoulder, steadies it for aim, and then depresses a trigger atop the launcher in front of the rear sight. The rocket within is ignited, and completely consumes its fuel before leaving the tube at between 150-200 meters per second. Once out of the tube, six fins unfold at the back of the rocket to stabilize it in flight, although it is unguided. The exhaust gases from the rocket reach over 1,600 degrees Fahrenheit, which makes the LAW unsafe to use in an enclosed space, unlike other systems such as the Armbrust.
The M72 is most comparable in effects and use to the Soviet RPG-7, although the RPG-7 utilizes a reusable launcher and a packaged 'booster charge' behind the rocket to throw it farther from the operator before ignition, since the rocket burn on the RPG is somewhat longer.
Although the rocket will reach a range of around a kilometer if allowed, it is considered to be effective against a stationary target at only between 10 and 200 meters. Longer than that and the unguided rockets are likely to miss their aimpoints; and even 10 meters is 'danger close' for the firer. Each round costs approximately $1,000 US to procure, which is fairly cheap for an organic anti-armor capability, however light.
More modern armored vehicles have made the M72 LAW obsolete, as its warheads are unable to penetrate even their thinner side and rear armor. However, that doesn't mean it is useless. In Vietnam, the troops discovered that while there weren't an awful lot of tanks to shoot at, there were all manner of bunkers, trenches, buildings and fortifications - and the M72 is just dandy at blowing the ever-loving heck out of structures. As a result, a large number were procured and issued to troops for use in clearing fortifications. The British Army went so far as to produce a new warhead for the M72, one which contained a kilo of high explosive rather than the usual one-third of a kilo, for use against buildings. They renamed it 'LASM' for 'Light Anti-Structures Missile.' The U.S. Army refers to these as LAW also, although here LAW stands for 'Light Assault Weapon.' The LAW was replaced in U.S. service in the late 1980s by the AT4 and SMAW. However, as the U.S. has become involved in urban combat in Iraq and Afghanistan, the reliable LAW has been pulled out of storage and re-issued for use against structures and light vehicles.
The LAW is a familiar sight in film. Dirty Harry uses one in the movie The Enforcer, and D-FENS (Michael Douglas's character) is instructed in the use of one by a local kid in Falling Down.