Photo shows work being done on the Japanese Naval code J-25 by Station HYPO in Hawaii. The Japanese order to prepare for war was sent in J-25 prior to the attack on Pearl Harbor, but decoders had been ordered to suspend work on the Naval code and focus efforts on the diplomatic code. Later, enough of J-25 was broken to be used as an advanced warning to the Japanese attack on Midway. NSA photo.
The U.S. Fleet stationed at Pearl Harbor approximately one month prior to the Japanese attack. An aircraft carrier is also visible at the top of the row of battleships (left side of Ford Island in this photo). Thees carriers were away during the actual attack. US Navy photo.