 In June 1943, following the outbreak of war with Japan, he was given command of the tactical (destroyer) component of RAN-US Navy Task Force 74.From his immediate command, HMAS "Warramunga", Dechaineux commanded operations in waters around Australia and New Guinea, including support for amphibious landings, such as those in the Admiralty Islands.He was promoted to Captain on 31 December 1943.