During the Second World War, Whitaker was awarded the Distinguished Service Order at the rank of captain for his achievement in the Dieppe Raid in August 1942. He was the only one of the 100 officers who landed on the beach to fight his way into town and escape unwounded. As a lieutenant colonel, Whitaker commanded the 1st Battalion, The Royal Hamilton Light Infantry–Canadian Army Active from February 17, 1944 until July 17, 1944 and from September 15, 1944 until March 29, 1945, throughout most of the fighting in northwest Europe. On 16 October 1944, during the Battle of the Scheldt, Whitaker took the village of Woensdrecht, which presented particular problems for the Canadians in their advance along the banks of the river Scheldt. He won a second Distinguished Service Order in February 1945 for leadership in the Battle of Goch-Calcar Road during Operation Veritable