The distinguished medical mentors Dunlop met in London, Professor Grey-Turner and Sir Thomas Dunhill, impressed him with their dedication to their job and he resolved to emulate their example.

During the Second World War, Dunlop was appointed to medical headquarters in the Middle East, where he developed the mobile surgical unit.

In Greece he liaised with forward medical units and Allied headquarters, and at Tobruk he was a surgeon until the Australian Divisions were withdrawn for home defence.

[14] Because of his leadership skills, he was placed in charge of prisoner-of-war camps in Java, and was later transferred briefly to Changi, and in January 1943 commanded the first Australians sent to work on the Thai segment of the Burma-Thailand railway where prisoners of the Japanese were being used as forced labourers to construct a strategically important supply route between Bangkok and Rangoon.

Conditions in the railway camps were primitive and horrific—food was totally inadequate, beatings were frequent and severe, there were no medical supplies, tropical diseases were rampant, and the Japanese required a level of productivity that would have been difficult for fully fit and properly equipped men to achieve.

A courageous leader and compassionate doctor, he restored morale in those terrible prison camps and jungle hospitals.

[15] He is depicted in a lighter moment during these terrible times on a birthday card painted by Ashley George Old for Major Arthur Moon and now held at the State Library of Victoria.

[23] His image is on the 1995 issue Australian fifty cent piece with the words "They Served Their Country in World War II, 1939 – 1945".