An evolution of the M1, the M9A1 was part of the "Bazooka"/"Stovepipe" line of shoulder fired anti-tank rocket launchers. The first of its kind, the Bazooka was a massive shift in how infantry dealt with tanks and armored vehicles and replaced the then underpowered anti-tank rifles of the inter-war era with a shaped charged rocket that could cope with the armor plating of the day. While other designs have come about, the basic principles are still in use today, and "bazooka" is still a recognized nickname for the entire class of weapon. The M9A1 was introduced in 1944 and would see America through the close of World War II. Constructed from two sections of steel tubing, the launcher could be broken down for storage and transport, with a flip-out optical sight for aiming and an integral magneto in lieu of an ignition battery. Both halves are marked "M9A1" near the junction point, and the serial number near the breech.