Central Bureau did not break any high level Japanese Army codes until mid-1943 success with the Water Transport Code. In January 1944, one main line Japanese Army code was broken with help from a buried trunk found at Sio, New Guinea, left by retreating Japanese Army troops of the 20th Division. The Bureau spent a day drying the damp pages, and the flood of decoded messages that ensued meant that MacArthur has to ask the US Navy for assistance (the Japanese thought that the papers had been destroyed).