Before departing Singapore, the Japanese ships, which were designated the Completion Force, were loaded with supplies of oil and other important raw materials. This formed part of an effort to run increased quantities of supplies through the Allied blockade of Japan before the country was cut off from its empire. The Allies had learned of the Completion Force's composition and goals through intelligence gained from decrypting Japanese radio signals, and plans were developed for coordinated attacks on it by submarines and United States Army Air Forces (USAAF) aircraft. As part of these preparations, 26 submarines were eventually positioned along the ships' expected route.