Back in the early days of WWII, the German Army brought Blitzkrieg, or Lightning War, to bear upon its enemies in Europe. This combination of tanks and infantry defeated every enemy on the Continent. Even before the US entered WWII, our Army knew they would have to find a way to counter this tactic. One big issue was, how does an infantry unit defeat tanks.
Each infantry regiment had an anti-tank company, armed with 18 towed anti-tank guns. This was a start, but still, something more was needed. What the Army really wanted was a weapon that could be carried by a small team of men, say 2 or 3, and give each company its own chance at defeating tanks. Right about this time, the HEAT warhead was developed. In fact, the Army had a large number of HEAT warheads in production. They just didn’t know what to do with them. They were 2.36 inches in diameter, which is 60mm, so there is some supposition they may have planned to make them mortar rounds. But mortars aren’t really accurate enough to attack tanks. Then the Army came up with a HEAT hand grenade. The obvious problem with that was you had to get pretty damn close to a tank to hit it with a grenade.
By a happy coincidence, the Army had two young officers, CPT. Leslie Skinner and LT. Ed Uhl working on a battlefield rocket system. They had a rocket that worked well, but no warhead. Much like the birth of a Reese’s Peanut Butter Cup, once they got the rocket and the warhead together, great things were happening.
The M1 Rocket Launcher was soon known far and wide as the Bazooka, since it faintly resembled a homemade musical instrument by the same name, made popular by comedian Bob Burns. The Bazooka worked. It gave infantrymen a fighting chance at destroying enemy tanks without sacrificing themselves. As the war went on, the Germans, facing huge numbers of Sherman tanks, copied the Bazooka and named it the Panzerschreck. Then they came up with the idea of making a disposable, one shot version, which they called the Panzerfaust.
The bazooka continued in service long after WWII, but the Army liked the idea behind the Panzerfaust. After much tinkering, the Army started to issue the M-72 Light Anti-tank Weapon, or LAW. Now, in Vietnam, there weren’t a lot of enemy tanks. But there were a lot of bunkers. And it just so happens that a LAW is a dandy way of taking out a bunker, much safer than the prescribed method of crawling up to it and throwing a grenade inside.
The LAW was a collapsible fiberglass and aluminum tube with a 66mm HEAT rocket inside. Pop it open, arm it, shoot it, throw away the tube. Easy as pie. The LAW was light enough that just about every soldier could carry one and in a pinch, a grunt could carry several of them. It was such a handy weapon, it is one of the few occasions of the Russians copying it. They call their version the RPG-18.
But by the late 1980’s, the LAW was getting long in the tooth, and the 66mm warhead was too small to take out modern tanks. Something bigger was needed. The Army went shopping. After trying several European rocket launchers, they settled on the 84mm Swedish AT4.
After some tweaks, the AT4 was introduced as the M136 Rocket Launcher. Still, everyone calls it the AT4. The AT4 has a bigger, faster rocket and warhead, longer range than the M72, and by virtue of its greater speed, is more accurate. I still wouldn’t want to try to take out a main battle tank with it, but for taking out a bunker, or a sniper hiding in a building, well, it is just the ticket.
Update: Someone did a google search asking what the “4” in AT4 stood for. Nothing. AT4 is a phonetic play on the caliber of the cartridge, 84mm. Say A T 4 and think “eighty-four.”