When Lord Sysonby joined the British Army, he chose the local 'County' regiment, the Queen's Royal Regiment (West Surrey), otherwise known as the West Surreys. He served initially in the Territorial Army, in the 5th Battalion, Queen's Royal Regiment, part of the 131st (Surrey) Infantry Brigade. During the Second World War, Lord Sysonby volunteered for the Commandos became a Commando officer and rose to the rank of Lieutenant-Colonel. He was decorated with the DSO in 1940 during the Battle of France and retreat to Dunkirk where he was evacuated.