Cracking the others was a constant challenge until near the war's end. And there were the constant problems of maintaining Allied code security and of disguising the true source of decoded intelligence. These reports and documents, which originated primarily with the military and diplomatic units directly involved, were brought together by the National Security Agency. The Pacific Theater This, the largest part of the collection, includes voluminous coverage of the intelligence background of the Pearl Harbor attack and extensive series on the role of radio intelligence in tactical operations and submarine warfare. The role of intelligence in the victory at Midway is analyzed at length.
Several histories focus on Japanese relations with Germany, the USSR, China, and southeast Asia.
Periodic Order of Battle reports and radio intelligence unit reports are also included. This part contains many reports on the Battle of the Atlantic, stressing submarine warfare and the histories of various radio intelligence units, as well as studies of liaison with the British and Soviets, of German blockade runners, and of strategic bombing operations. Several reports describe Mediterranean Theater activities. Organization and Administration Army, navy, and several civilian intelligence agencies competed more often than they cooperated in the war effort. But there were important examples of mutual help and there was work enough to give all parties room to grow.