All Hell Let Loose_ The World at War 1939-1945 - Max Hastings [233]
The picture of enemy operations provided by Ultra was always incomplete, but it offered a reliability no human intelligence, or ‘humint’, provided by spies could match. For instance, the Allies could launch D-Day on 6 June 1944 confident that the enemy was still oblivious of their objective and timing. Churchill permitted some Ultra information about the Eastern Front to be passed to Moscow. Stalin was never officially informed of the Bletchley Park operation, but Moscow was well briefed by British traitors, who supplied their NKVD handlers in London with a steady flow of decrypts.
Full Anglo–American intelligence-sharing began only in 1943. The United States had broken the Japanese diplomatic cipher before the war, but their handling of Ultra never matched the inter-service integration achieved by the British, partly because of army–navy rivalry. The US Army ran its own decryption operation at Arlington Hall, Virginia, eventually employing 7,000 staff. The USN team, based in bleak subterranean quarters at Fourteenth Naval District, Pearl Harbor, was led by Commander Joseph Rochefort, the brilliant Japanese-speaker, cryptanalyst and intuitive thinker who contributed so much to victory at Midway. Rochefort’s men read some messages in the Japanese navy’s JN-25 operational cipher soon after the outbreak of war, and achieved fragmentary breaks at vital moments in 1942, which proved the most important Ultra achievements of the Pacific war. Thereafter, however, for some months JN-25 defied Rochefort’s team, leaving naval intelligence dependent upon coast-watchers and traffic analysis. In 1943 the operational code was again broken, and provided a stream of data for the rest of the war.
Bletchley Park and Arlington Hall played key roles in breaking Japanese army codes in 1943, the first being that of military attachés overseas. Captures of Japanese codebooks laid open bulk military signal traffic in 1944. Whereas in January that year Arlington Hall read fewer than 2,000 of the enemy’s army messages, in March this increased to 36,000, decisively influencing MacArthur’s New Guinea strategy. Interception of Japanese communications faltered during the 1944–45 Philippines campaign, when the army’s main codes changed, causing a further break in decryption. In general, US naval operations were more importantly influenced by Ultra than were those of the armies in the Pacific campaigns. No codebreaking achievement could eliminate the difficulties of assaulting strongly defended enemy positions. But the collective contribution of US and British cryptanalysts to the war effort was greater than that of any other such small body of men in history. Their operations provided the supreme example of the Western Allies’ imaginative integration into the war effort of their cleverest civilian intellects.
In the autumn of 1942, Churchill was passionately impatient for Eighth Army to attack. Once the Torch landings took place, the glory of every subsequent British success would be shared with the Americans. Alexander and Montgomery were relentlessly chivvied from London, though the foxy little field commander stuck to his own timetable. A cold, incisive, self-consciously professional soldier, ‘Monty’ was determined to impose on British operations an order and discipline which had hitherto been absent. He has sometimes and not unjustly been described as ‘a good World War I general’, most comfortable with limited set-piece operations. His most conspicuous attribute was ‘grip’: between August and October 1942, in a remarkable fashion he revived the confidence of the desert army.