Not knowing which of the many islands would be the American target, the Japanese would have to disperse their strength by garrisoning many islands that would never be attacked. An island like Eniwetok in the Marshall Islands, would, Ellis estimated, require two regiments, or 4,000 Marines. Guided by Marine observer aircraft, and supplemented by Marine light bombers, warships would provide enough firepower so that Marines would not need any heavy artillery (in contrast to the Army, which relied heavily on its artillery). Shelling defended islands was a new mission for warships. The Ellis model was officially endorsed in 1927 by the Joint Board of the Army and Navy (a forerunner of the Joint Chiefs of Staff).