The development of the Bazooka was born of 2 different weapons - The Recoilless Rocket and the Shaped Charge Warhead. Following work done by Dr Robert H. Goddard towards the end of WW1, he successfully demonstrated a Tube Launched Rocket at the Aberdeen testing Grounds in Maryland. But just a few weeks later the War ended and interest wained. Goddard continued to work on the weapon for the War Department in a part time capacity until the early 20's when he lost interest. This left others to pick up where he left off. Henry Mohaupt, a Swiss immigrant, was working on a Rifle Launched Grenade, the M10. This was the best weapon of it's type at the time being able to penetrate 100mm of Armour. However because of it's weight it was found unsuitable as a Rifle Launched weapon. A smaller version was developed, the M9 which was suitable for Rifle Launching.