Called up to the British Army in 1942, Phillips rose to the rank of Lance-Bombardier in the Royal Artillery. Due to his acquired upper class accent, Phillips was selected for officer training at Catterick and duly commissioned as a Second Lieutenant in the Royal Artillery in 1943. In his autobiography, he would recall that his anti-aircraft battery destroyed numerous German V1 flying bombs launched against the UK during the period. He was transferred to the Durham Light Infantry in 1944 but was later declared unfit for service just before D-Day after being diagnosed with a neurological condition that caused partial paralysis. He was initially sent to a psychiatric hospital in error but was then sent to the correct facility for treatment.