Macdhui was built by the Clydeside shipbuilders Barclay Curle & Co and launched 23 December 1930. Of 4561 gross tons length 341ft. and breadth 51ft she was registered in Sydney and carried an Australian crew. She commenced trading between Sydney, Papua and New Guinea in May 1931 providing a significant improvement in that service and remaining engaged therein beyond Japan's entry to the Second World War.
Though German Commerce Raider threats a few months before had not harmed her, in December 1941 Macdhui (with Neptuna which had evacuated a large number of civilians from Manila in the Philippines and transhipped them at Port Moresby) went to Rabaul and evacuated women and children from New Britain and the outlying islands and plantations, as many as possible, ahead of the Japanese advance and occupation. She was then taken over by the Australian Government for the transportation of troops and their logistic supplies for the defence of New Guinea, operating between Sydney and Port Moresby.
Evidence of Japanese atrocities and executions helped accelerate evacuation plans for all women and children from the South Pacific area. Large numbers of civilians were landed in Australia from merchant ships including Macdhui. In many cases small ships brought them to safety at Port Moresby, whence they were taken to Townsville Macdhui being heavily involved. It was an activity relatively little publicised, but of epic proportions. Those evacuated included four hundred survivors from the sinkings by German raiders in the area who had been left stranded on the island of Emirau near Kavieng on New Britain.