Mountbatten was an expert in communications in the Royal Navy when the war began. In 1939 he was given command of the 5th Destroyer Flotilla assigned to the defense of Britain, and participated in the evacuation of Allied troops from Norway. In April 1941 he took his fleet to Malta and in May saw action off Crete, in which his flagship, HMS Kelly, was sunk. Shortly after he became Adviser on Combined Operations and was involved in preliminary planning for the projected invasion of Europe. He continued his planning activities as a member of the Chiefs of Staff Committee, working on the raids at St Nazaire (March) and Dieppe (August) and the Allied North Africa Landings of November 1942. Mountbatten also attended the Casablanca Conference in January 1943 and the Quebec Conference (July) at which the Allied command in Southeast Asia was reorganized.
Mountbatten became Supreme Allied Commander of this new Southeast Asia Command in October 1943. He lacked ships, landing craft and other equipment and therefore decided to concentrate on a land campaign. He spent the remainder of 1943 building up a secure base in India with improved communications which could be used for the campaign in Burma which began in December 1943. Mountbatten carried out these preparations with flair and a real feeling for public relations which enormously increased morale. The campaign itself, directed by General SLIM, was very successful despite limited resources, highlighted by the countering of a major Japanese offensive at Kohima and Imphal in February-March 1944 and the capture of Mandalay in March 1945. Burma was completely reconquered by May 1945. In September Mountbatten accepted the surrender of 750,000 Japanese at Singapore.
Mountbatten was a popular General because of his showmanship and a successful one because of his great capability,belief in science and technology and his ingenuity in confronting problems.