The Grand Fleet was the main fleet of the British Royal Navy during the First World War. The actual strength of the fleet varied through the war as new ships were built and others were sunk, but the numbers steadily increased as the war progressed and the margin of superiority over the German fleet progressed with it. After America entered the war, US Battleship Division Nine was attached to the Grand Fleet as the Sixth Battle Squadron, adding four, and later five, dreadnought battleships. Author and Admiral John Rushworth Jellicoe fought in the Anglo-Egyptian War and the Boxer Rebellion and commanded the Grand Fleet at the Battle of Jutland in May 1916 during the First World War.