During the Second World War, Todd joined the British Army receiving a commission in 1941. Initially, he served in the King's Own Yorkshire Light Infantry before joining the Parachute Regiment and being assigned to the 7th (Light Infantry) Battalion as part of the British 6th Airborne Division.
On 6 June 1944, as a Captain, he participated in the British Airborne Operation Tonga during the D-Day landings.
Capt. Todd was among the first British officers to land in Normandy as part of Operation Overlord. His battalion were reinforcements that parachuted in after glider forces had landed and completed the main assault against Pegasus Bridge near Caen.
He later met up with Major John Howard on Pegasus Bridge and helped repulse several German counter attacks.
As an actor, Todd would later play Howard in the 1962 film The Longest Day.