Central Bureau at 21 Henry Street, Ascot, in Brisbane decrypted a Japanese Army Air/Ground signal intercepted by 51 Wireless Section in Darwin that contained Admiral Isoroku Yamamoto's itinerary for an upcoming trip to Rabaul. Admiral Yamamoto, was the Commander in Chief of the Combined Japanese Fleet, the architect of the attack on Pearl Harbor. Central Bureau reportedly sent the decrypted message to FRUMEL where it was reportedly translated by a U.S. Navy linguist. Although Central Bureau may have decrypted the message, the interception of his flight was based on decrypts of Japanese naval messages by FRUPAC/Station HYPO in Hawaii, FRUMEL, OP-20-G in Washington and Station AL on Guadalcanal. Major Lasswell USMC in Hawaii decrypted the Japanese Naval message first and Captain Layton (Pacific Fleet Intelligence in Hawaii) gave it to Admiral Nimitz who authorized a shootdown attempt after determining from ComNavAirSoPac that it could be done with by one of his Army Air Corp units on Guadalcanal.