When the First World War (1914–18) broke out, Edward had reached the minimum age for active service and was keen to participate.[11] He had joined the army, serving with the Grenadier Guards, in June 1914, and although Edward was willing to serve on the front lines, the Secretary of State for War, Lord Kitchener, refused to allow it, citing the immense harm that would occur if the heir to the throne were captured.[12]
Despite this, Edward witnessed trench warfare firsthand and attempted to visit the front line as often as he could, for which he was awarded the Military Cross in 1916. His role in the war, although limited, led to his great popularity among veterans of the conflict.[13] As of 1911 he was also a Midshipman in the Royal Navy, making Lieutenant in 1913. Edward undertook his first military flight in 1918 and later gained his pilot's licence.[14] On his succession he became Admiral of the Fleet in the Navy, Field Marshal in the Army, and Marshal of the Royal Air Force.[15]