This book provides a brief description of combat operations in all naval theaters of the Second World War - in the Atlantic, North, Mediterranean, Baltic and Black Seas, in the Arctic, in the Indian and Pacific Oceans. The actions of squadrons and flotillas, raiding ships, carrier-based aircraft, submarines, anti-submarine defense forces during the main naval campaigns and operations of the period 1939-1945. Considerable attention was paid to the conduct of convoys and landings. The tactics of naval battles are considered. The book is addressed to a wide range of readers interested in the military history of the 20th century, as well as the history of naval art.