Deane became a surgeon at the Adelaide Hospital, Dublin. He was then commissioned into the Royal Army Medical Corps in 1911. In 1913, he was posted to India and served in Burma. He was sent to Meerut at the start of the First World War. He went to France with the Garhwal Brigade of the Indian Expeditionary Force. They d in Marseilles in September 1914. He was then sent immediately to the Western Front. There he served first with the 20th Field Ambulance. Then he served as a medical officer of the 2nd Battalion, The Royal Leicestershire Regiment. His unit saw much active service. On 22 August 1915, he was awarded the Military Cross after running out under machine gun fire to rescue four men who had been wounded by artillery fire. A month later, his regiment participated in the Battle of Loos, and was almost entirely destroyed. He was shot dead after going to help some injured soldiers. His action earned him a mention in dispatches.