An expert in the field of submarine warfare, Horton was given command of the Reserve Fleet from 1937 to 1939. At the beginning of World War II he was in command of the difficult and dangerous Northern Patrol and in January 1940 became Flag Officer Submarines. In 1942 he was appointed Commander in Chief of the Western Approaches which meant that he was responsible for seeing that the convoys carrying supplies to and from North Africa could cross the Atlantic safely. Confronted with 400 German U- Boats, this was to prove a difficult task. Fortunately the ‘air gap’ in the midAtlantic was closed and more escorts were made available. By May 1943 the shrewd and competent Horton was able to turn the Battle of the Atlantic into the Allies’ favor.