The ship was converted at Sydney to carry troops. She transported both Australian and American troops to Port Moresby, Milne Bay and Oro Bay in New Guinea. On 11 July 1942 she had arrived at Milne Bay with Brigadier John Field and the 7th Brigade Group as "Milne Force" to protect the developing port and airfields. She was in Milne Bay the night before and left the morning of the Japanese landings and the first ship to reinforce Milne Bay during the Japanese attempt to take the airfields there. "Tasman" made three later attempts to enter the bay, being driven off by Japanese naval vessels. The ship was escorted by during these New Guinea operations.