After the disaster at Pearl Harbor Roosevelt turned to the most aggressive sailor available, Admiral Ernest J. King (1878-1956). Experienced in big guns, aviation and submarines, King had a broad knowledge and a total dedication to victory. He was perhaps the most dominating admiral in American naval history; he was hated but obeyed, for he made all the decisions from his command post in the Washington, and avoided telling anyone.[124] The civilian Secretary of the Navy was a cipher whom King kept in the dark; that only changed when the Secretary died in 1944 and Roosevelt brought in his tough-minded aide James Forrestal.[125] Despite the decision of the Joint Chiefs of Staff under Admiral William D. Leahy to concentrate first against Germany, King made the defeat of Japan his highest priority. For example, King insisted on fighting for Guadalcanal despite strong Army objections.[126] His main strike force was built around carriers based at Pearl Harbor under the command of Chester Nimitz.[127] Nimitz had one main battle fleet, with the same ships and sailors but two command systems that rotated every few months between Admiral Bull Halsey[128] and Admiral Raymond A. Spruance.[129] The Navy had a major advantage: it had broken the Japanese code.[130] It deduced that Hawaii was the target in June 1942, and that Yamamoto’s fleet would strike at Midway Island. King only had four carriers in operation; he sent them all to Midway where in a miraculous few minutes they sank the Japanese carriers. This gave the Americans the advantage in firepower that grew rapidly as new American warships came on line much faster than Japan could build them. King paid special attention to submarines to use against the overextended Japanese logistics system. They were built for long-range missions in tropical waters, and set out to sink the freighters, troop transports and oil tankers that held the Japanese domains together.[131] The Southwest Pacific theatre, based in Australia, was under the control of Army General Douglas MacArthur; King assigned him a fleet of his own without any big carriers.