During the First World War, Fuller was a staff officer with the Home Forces and with VII Corps in France, and from 1916 in the Headquarters of the Machine-Gun Corps' Heavy Branch which was later to become the Tank Corps. He helped plan the tank attack at the 20 November 1917 Battle of Cambrai and the tank operations for the Autumn offensives of 1918. His Plan 1919 for a fully mechanised offensive against the German army was never implemented. After 1918 he held various leading positions, notably as a commander of an experimental brigade at Aldershot.
During the First World War, Fuller was a staff officer with the Home Forces and with VII Corps in France and from 1916 in the Headquarters of the Machine-Gun Corps' Heavy Branch which was later to become the Tank Corps He helped plan the tank attack at the 20 November 1917 Battle of Cambrai and the tank operations for the Autumn offensives of 1918 His Plan 1919 for a fully mechanised offensive against the German army was never implemented. After 1918 he held various leading positions, notably as a commander of an experimental brigade at Aldershot.