Human intelligence, intercepted messages, traffic analysis, and maritime reconnaissance supplied different kinds of information. Traffic analysis tracked the volume and routes of signals to identify important locations and relationships between commands, even without reading message contents. Its personnel and data requirements were much larger than those of the dramatic decrypts that dominate popular accounts. Aircraft, cruisers, and submarines added sightings and photographs to that communications picture. Midway's uncoded water-supply report provided a controlled clue: analysts could watch for references to water in Japanese messages and test which location Japan intended to attack.
Chapter · 11:31-16:01
Intelligence sources and the Midway water ruse
Traffic analysis, decrypts, human sources, and reconnaissance supplied different clues; the Midway water report tested the target identified in Japanese messages.