Early in the afternoon of 27 November 1941, Admiral Husband E. Kimmel wanted to see Commander Joe Rochefort. Perplexed by Japanese moves in the Pacific, besieged by troubling and often confusing communications from Washington, D.C., and looking for answers no one else seemed to have, Kimmel sought out the gifted, if sometimes acerbic, officer who ran Station Hypo, the U.S. Navy’s cover name for its codebreaking unit at Pearl Harbor.
Rochefort actually was at the heart of some of the activity besetting Kimmel. A day earlier the commander had transmitted an urgent 220-word dispatch to naval brass in Washington, with copies to Kimmel and Asiatic Fleet commander Admiral Thomas C. Hart in Manila. The memo described movements of the Imperial Japanese Navy (IJN) in the far Pacific. It disclosed that key elements of the IJN’s mighty Second and Third Fleets were moving south into the South China Sea.