On July 15, Saipan (in the Northern Mariana Islands) was captured by Allied forces. The capture of Saipan made it possible for the United States Army Air Force to attack Japan itself, using B-29 Superfortress bombers. After the fall of Saipan, the Japanese commanders knew that the Allies would try to capture the Philippines next. The Philippines were very important because they were located between the oil fields of Southeast Asia and Japan. If Japan lost control over the Philippines, they would have little fuel left for their ships. On October 17, the Allies started the attack on the Philippines in the Battle of Leyte Gulf.