April 30, 2025: This is a tale of unexpected lost opportunities and equally unexpected decrypts that changed the course of many battles in World War II. The unexpected opportunities went to the Germans and Japanese. In the Pacific the Japanese had occupied Saipan since 1914. The island's 26,000 civilian residents made a living raising sugar cane and turning it into sugar.

After the Japanese defeats in early 1942, Japan began to fortify islands that were deemed candidates fop American amphibious attacks. Saipan was invaded in mid-1944 and, during the early stages of the battle, the Japanese captured two M-109 U.S. army cryptography documents and got the data back to Japan. These documents enabled the Japanese to read American military communications. The Japanese had another edge. Their radio Direction/Finding and traffic analysis systems enabled them to detect American air raids farther out than the best radar systems available to the U.S. Navy at the time. This explains why the Japanese Kamikaze suicide aircraft attacks often came at surprising times and from unexpected directions. U.S. Navy air defenses were mostly able to cope with these attacks, despite losing many smaller ships sunk or seriously damaged.

The Japanese maintained undersea cables between many of their occupied islands in the Pacific. The Americans did not discover until after the war how well informed the Japanese commanders of these islands were. Details of American attacks on Saipan and in the Philippines were known to the Japanese and that explains why Japanese counter attacks often showed up when the Americans were not expecting them. At the time American army and navy leaders thought the Japanese were just lucky. It was only after the war that evidence of Japanese code breaking was discovered.

The only U.S. forces that countered the Japanese crypto edge were commanded by General MacArthur. He had a group of Australian as well as American crypto and communications experts who sorted out what the Japanese were doing and how they did it. The navy ignored MacArthur and the impact of Japanese sailors looting all the crypto equipment from the American submarine Darter which was grounded on a shoal of the Filipino island of Palawan in late 1944. The Japanese destroyer that was pursuing Darter went aboard the sub after the crew abandoned it and found that all the Americans crypto codes and machines were intact. This material was taken and enabled the Japanese to read U.S. Navy encrypted traffic for the rest of the war. This was another reason for the relative success of Kamikaze aircraft to show up and attack when least expected.

The signals intelligence captured by the Japanese enabled them to find and attack U.S. Navy command ships during the Luzon, Iwo Jima and Okinawa operations. Another unexpected source of Japanese success was the help they received from their German allies, who captured American codebooks and ciphers during the mid-1943 Sicily campaign. The Germans passed this on to the Japanese. After the war all this successful Japanese cryptography and counterintelligence activity was discovered. The Americans were amazed and humbled at how adept the Japanese had been at breaking codes, and successfully covered it up for 65 years. The Japanese were equally shocked to discover that the Americans had broken many of the Japanese codes. This was a major reason the Americans won the pivotal battle of Midway in June 1942. This destroyed most of the Japanese aircraft carriers and put Japan on the defense years before they expected that to happen.