In August 1925 Nave "loaned" to the British
Royal Navy. He was sent to Hong Kong and posted to the heavy cruiser . Nave expected to be employed as an interpreter, but instead was presented with intercepted coded Japanese naval signals and ordered by the
Commander-in-Chief, China, to break them. Within two months Nave had not only broken the code, but had also worked out the
Imperial Japanese Navy's radio protocols and relay system, and the organisation of their various commands. He also broke another code before his period of loan service was completed The loan was promptly renewed in December 1927 and Nave was assigned to the Japanese desk in the
Government Code and Cypher School in England. There he broke the code of the Japanese
naval attaché, which meant that during
London Naval Conference of 1930, the Admiralty were fully aware of the Japanese negotiating position, and also the Japanese Navy's strategy for fighting a war with the United States. and on 29 August 1930 "in view of his exceptional qualifications and experience in certain specialist duties" he was transferred to the
Royal Navy. This required an
Order in Council from the
Privy Council because of the different systems of pay and pensions in the two services. Nave was the first officer to be transferred from the Royal Australian Navy to the Royal Navy. Nave's codebreaking career continued, serving in the
China Fleet and in London. He was promoted to paymaster commander on 30 June 1937, and assigned to the code-breaking unit of the
Far East Combined Bureau (FECB), a tri-service intelligence organisation based in Hong Kong. There his team successfully broke a series of Japanese naval codes until the introduction in early 1939 of "Naval Code D", designated by the US Navy "
JN-25". By early December 1939, FECB had been relocated to
Singapore, and the code was beginning to relinquish some of its secrets. However, the pressure of work had begun to take its toll on Nave's health, and in early 1940 he was diagnosed as suffering from
tropical sprue, and was sent back to Australia to recuperate. Sick, and with a "heavily pregnant" wife, he did not want to return to Singapore. On medical advice Nave did not return to the tropics instead setting up a small RAN cryptographic unit in
Victoria Barracks, Melbourne. The unit had a core of naval personnel, with a number of university academics and graduates specialising in classics, linguistics and mathematics, e.g.
Athanasius Treweek and
Arthur Dale Trendall. In May 1941 Nave's unit was combined with personnel from the Australian Army and designated the Special Intelligence Bureau (SIB). They had some successes, reading Japanese diplomatic traffic from South America, and also breaking JN-4, the operational code for submarines. In early 1942 SIB became part of the "
Fleet Radio Unit, Melbourne", (
FRUMEL), an "inter-naval" (joint American-Australian-British) cryptographic unit, and moved to the "Monterey" apartment building in Queens Road. FRUMEL was commanded by USN Lieutenant Rudolph Fabian, formerly of
Station CAST in the Philippines. Despite continued success (Nave had warned, a month before it happened, that the Australian base at
Milne Bay, at the eastern tip of
New Guinea, was to be invaded in late August 1942, so the base was reinforced, and the subsequent
Battle of Milne Bay was decisively won by U.S. and Australian forces – the first time the Japanese had been defeated on land by the Allies) Nave was reportedly forced out of FRUMEL and "Monterey" by Fabian, who apparently regarded him as a "security risk", because Nave wanted to cooperate with the "inter-army" unit, the
Central Bureau, based at Brisbane. According to his staff, Nave often kept keys to new codes passed on by the Americans and British to himself, which might have been acceptable as a training exercise in peacetime, but not in time of war. Treweek said: "We always looked forward to his day off. We'd get the keys to his safe and find all this material in there." Nave also had difficulties with his superior, Commander Rupert B. M. Long, the Director of Naval Intelligence, whom he considered a man of no great ability. Nave subsequently joined Central Bureau in early 1943. Joe Richard, a Central Bureau veteran, said later that "[i]f Fabian did not want Nave, the U.S. Army codebreakers were very happy to have him ... Fabian's dislike of Eric Nave was very fortunate for us. Nave became an indispensable person" in "reading air-to-ground messages containing the weather" which "gave away the intended target for the day." Nave also created a system of field units to intercept operational messages and advise field commanders of Japanese movements and intentions, a model of successful integration of intelligence with operations. Nave was promoted to the
acting rank of captain on 12 October 1944. When Central Bureau moved forward to the Philippines in 1945, Nave was left behind to write the unit's official history and to close down the organisation in Brisbane. ==Post-war career==