first. For instance, Germany had been at war with the UK since 1939, and with the USSR since June 1941, without Japanese assistance. There had been a serious, if low-level, naval war going on in the Atlantic between Germany and the U.S. since summer of 1941, as well. On October 17 a U-boat torpedoed a U.S. destroyer, USS Kearny, inflicting severe damage and killing eleven crewmen. Two weeks after the attack on the Kearny, a submarine sank an American destroyer, USS Reuben James, killing 115 sailors. Nevertheless, it was only Hitler's declaration of war on 11 December, unforced by treaty, that brought the U.S. into the European war. Clausen and Lee's Pearl Harbor: Final Judgement reproduces a Purple message, dated 29 November 1941, from the Japanese Ambassador in Berlin to Tokyo. A closing paragraph reads, "... He (Ribbentrop) also said that if Japan were to go to war with America, Germany would, of course, join in immediately, and Hitler's intention was that there should be absolutely no question of Germany making a separate peace with England. ..." While theorists who challenge the conventional view that the attack was a surprise treat this as a guarantee to join after Japan's attack, it can as easily be taken as a guarantee to come to Japan's aid, as Germany had done for Italy in Libya. Assertions that Japanese codes had already been broken U.S. signals intelligence in 1941 was both impressively advanced and uneven. In 1929, the U.S. MI-8 cryptographic operation in New York City was shut down by Henry Stimson (Hoover's newly appointed Secretary of State), citing "ethical considerations", which inspired its now broke former director, Herbert Yardley, to write a 1931 book, The American Black Chamber, about its successes in breaking other nations' crypto traffic. Most countries responded promptly by changing (and generally improving) their ciphers and codes, forcing other nations to start over in reading their signals. The Japanese were no exception. Nevertheless, U.S. cryptanalytic work continued after Stimson's action in two separate efforts: the Army's Signal Intelligence Service (SIS) and the Navy's Office of Naval Intelligence (ONI) crypto group, OP-20-G. Cryptanalytic work was kept secret to such an extent, however, that major commands such as the 14th Naval District at Pearl Harbor were prohibited from working on codebreaking by Admiral Kelly Turner. By late 1941, those organizations had broken several Japanese ciphers, such as J19 and PA-K2, called Tsu