High Quality Content by WIKIPEDIA articles! The Battle of Osan was the first engagement between United States and North Korean forces during the Korean War, on July 5, 1950. A U.S. task force of 400 infantry supported by an artillery battery was moved to Osan, south of the South Korean capital Seoul, and ordered to fight as a rearguard to delay advancing North Korean forces while additional U.S. troops arrived in the country to form a stronger defensive line to the south. The task force lacked both anti-tank guns and effective infantry anti-tank weapons, having been equipped with obsolescent 2.36-in. rocket launchers and a few 57mm recoilless rifles. Aside from a limited number of HEAT shells for the unit`s 105-mm howitzers, crew-served weapons capable of defeating the T-34 had not been distributed to U.S. Army forces in Korea.