From 1942 onwards, the efforts of Bomber Command were supplemented by the Eighth Air Force of the United States Army Air Forces, U.S. Army Air Forces units being deployed to England to join the assault on mainland Europe on 4 July 1942. Bomber Command raided by night and the US forces by day. The "Operation Gomorrah" raids on Hamburg (24 July 1943 – 29 July 1943) caused a firestorm leading to massive destruction and loss of life.