Political map of East Asia and the Western Pacific 4 December 1944 (Operation Ichi-Go): In early 1944 the US started preparing airfields in southeast China for B29 bomber raids on Japan (Operation Matterhorn). The Japanese responded with Operation Ichi-Go, a general offensive to capture the air bases and open a land route to Indochina. Although Ichi-Go succeeded, by this stage the US bombers were able to relocate to the Marianas and raid Japan from there (XXI Bomber Command).