During World War II, the Western Australian port of Fremantle was host to over 170 US, British and Dutch submarines. Braced for invasion and taking the war to the Japanese in South East Asia, these submarines made 416 war patrols between March 1942 and  August 1945. Many never returned. This episode of Backyard Battlefields is an interview with Lynne Cairns, author of 'Secret Fleets: Fremantle's World War II Submarine Base'