United States Army Air Forces (USAAF) units based in China attacked the Hong Kong area from October 1942. Most of these raids involved a small number of aircraft, and typically targeted Japanese cargo ships which had been reported by Chinese guerrillas. By January 1945 the city was being regularly raided by the USAAF. The largest raid on Hong Kong took place on 16 January 1945 when, as part of the South China Sea raid, 471 United States Navy aircraft attacked shipping, harbour facilities and other targets.