The United States had multiple rocket programs divided among the different branches of the American armed services, which meant that each force developed its own ICBM program. The Air Force initiated ICBM research in 1945 with the MX-774. However, its funding was cancelled and only three partially successful launches were conducted in 1947. In 1950, von Braun began testing the Air Force PGM-11 Redstone rocket family at Cape Canaveral. In 1951, the Air Force began a new ICBM program called MX-1593, and by 1955 this program was receiving top-priority funding. The MX-1593 program evolved to become the Atlas-A, with its maiden launch occurring June 11, 1957, becoming the first successful American ICBM. Its upgraded version, the Atlas-D rocket, would later serve as an operational nuclear ICBM and as the orbital launch vehicle for Project Mercury and the remote-controlled Agena Target Vehicle used in Project Gemini.

The US Air Force began research of ICBMs in what year?