The United States Navy sent a battleship group to Scapa Flow to join with the British Grand Fleet, destroyers to Queenstown, Ireland, and submarines to help guard convoys. Several regiments of US Marines were also dispatched to France. The British and French wanted American units used to reinforce their troops already on the battle lines and not waste scarce shipping on bringing over supplies. General John J. Pershing, American Expeditionary Forces (AEF) commander, refused to break up American units to be used as filler material. As an exception, he did allow African-American combat regiments to be used in French divisions. The Harlem Hellfighters fought as part of the French 16th Division, and earned a unit Croix de Guerre for their actions at Château-Thierry, Belleau Wood, and Sechault. AEF doctrine called for the use of frontal assaults, which had long since been discarded by British Empire and French commanders due to the large loss of life that resulted.