Mulgan held leftist political views and was alarmed by the rise of fascism in Europe and the response of the British government to it.
During this time, he wrote a series of articles on foreign affairs, titled "Behind the Cables", for the Auckland Star newspaper.
His view that war in Europe was inevitable led Mulgan to join the Territorial Army in 1938, and he was made second lieutenant in an infantry regiment.
[3] In 1943, Mulgan joined the Special Operations Executive and was sent to Greece in September to coordinate guerrilla action against the German forces.
After the German withdrawal in 1944, Mulgan oversaw British compensation to Greek families who had helped the Allied forces (the Liquidation Fund.).