Contents - Hirohito's War
12 Battle of the Coral Sea: The First Carrier ‘Shoot-Out’
[April 1942–May 1942]
[Maps: 12.1, 12.2]
The US Naval Intelligence Network (p 353) Japanese Carriers to the South Pacific (p 354) Preparation for Battle (p 355) Japanese Invasion of Tulagi Island (p 357) Maneuverings for a First Carrier to Carrier Battle (p 358) The Battle of the Coral Sea: First Blood to Admiral Fletcher [7 May 1942] (p 360) The Battle of the Coral Sea Continued: Shokaku Wounded, USS Lexingon Sunk [8 May] (p 364) Licking their Wounds (p 367) Bombers and Bombs (p 370) The Battle of Words (p 371)
The US Naval Intelligence Network: Unbeknownst to the Japanese, one of the main ingredients in their early war successes disappeared in the early months. ‘Surprise,’ their major weapon in the first few weeks of the Pacific War, was completely negated by the development of an American intelligence and decryption capability that the Japanese were never able to match. The tables were turned. The Americans, with remarkable speed, had developed an intelligence network and capability that meant that they now possessed the advantage of ‘surprise.’ It proved to be one of the key turning points of the war and perhaps the main reason why the US Navy was able to turn around its disastrous start to the Pacific War within little more than six months of Pearl Harbor.
Commander Edwin Layton was appointed Chief Intelligence officer to Admiral Husband Kimmel on 8 December 1940. His position was such, given the debacle of Pearl Harbor exactly a year later, that it would have been no surprise if Nimitz had dispensed with his services. In fact Kimmel and his intelligence team were never given access to the decryption transcripts PURPLE, the high level Japanese diplomatic code, which might have enabled them to raise a higher level of preparedness before the attack on Pearl Harbor. Nevertheless it speaks well of Nimitz’s man management skills that he retained existing staff and assessed them on the basis of the work they did for him. The retention of Layton was inspired. He proved to be adept at piecing together and analysing multiple pieces of intelligence information. Weeding out the ‘noise’ of intelligence that was often conflicting, Layton was able to predict Japanese movement with uncanny accuracy from listening posts set up around the Pacific. It was a far from easy task as the Japanese, as a precaution, would often transfer call signs between warships of different size in order to better hide their capital ships. It was a critical skill in the early stages of the Pacific War when the Japanese and American resources were so evenly matched. Superior intelligence would tip the balance in the US Navy’s favor.
Layton was half of a double act. Joseph Rochefort had become close friends with Layton when they had studied Japanese together in Tokyo from 1929 to 1932. While Layton specialized in intelligence analysis, Rochefort went on to specialize in cryptology. In 1941 he was sent to Hawaii by Commander Laurence Safford, head of the code and signal section of the Navy HQ in Washington known as OP–20-G. Rochefort set up the so-called HYPO Station (H for Hawaii) in a disused basement in Pearl Harbor’s new administration building; it was to become known as the ‘Dungeon.’