While the Japanese did enjoy some success in intercepting American radio traffic in the Pacific Theater of World War II, their effort would never compare to more sophisticated U.S. capabilities.
During the long night, the eve of one of the great carrier battles of the Solomons Campaign, radio intelligence monitors on board the Japanese aircraft carrier Shokaku overheard the enemy’s coded transmissions. They could not read the messages but these took the format of contact reports, and the signal strength was very high, indicating a nearby emitter. The inevitable conclusion was that Allied search planes had sighted the Japanese task force and were reporting its presence. Imperial Navy carrier commander Vice Admiral Chuichi Nagumo had been in a spirited debate with his chief of staff over whether the fleet should head toward Guadalcanal to smite Allied flotillas they assumed to be in waters off the Solomon Islands. Chief of Staff Rear Admiral Ryunosuke Kusaka advised caution.