Australia's first submarines, the AE1 and the AE2, were launched in 1913 and were manned by composite Australian and British crews.
At the outbreak of the First World War the two submarines were sent from Sydney to German New Guinea with the Australian Naval & Military Expeditionary Force and helped to capture the German colony. On 14 September, a day after the official German surrender of the colony, the AE1, commanded by Lieutenant Commander Thomas Besant, left Rabaul harbour to patrol Cape Gazelle and never returned. The fate of the submarine was never discovered but it is probable that it was caught on a coral reef and sunk.
The AE2, commanded by Lieutenant Commander H. S. Stoker, achieved fame for its operations in the Dardanelles. The AE2 was ordered to sail through the Dardanelles and disrupt Turkish shipping in the Sea of Marmora. No other submarine had yet managed to breach the Turkish defences but, in the early hours of 25 April 1915, the AE2 got past minefields and land-based guns. After torpedoing a Turkish destroyer it reached the Sea of Marmora. The AE2 remained at large for five more days before sustaining irreparable damage while under heavy fire. Stoker was forced to sink the submarine and surrender. He and his crew spent the rest of the war in Turkish captivity. Stoker was awarded the Distinguished Service Order after the war.
The wreck of the AE2 was located in June 1998. The AE1 has never been found.