During the 1930s, as the industrialization of the Soviet Union proceeded, plans were made to expand the Soviet Navy into one of the most powerful in the world. Approved by the Labour and Defence Council in 1926, the Naval Shipbuilding Program included plans to construct twelve submarines; the first six were to become known as the . Beginning 4 November 1926, Technical Bureau Nº 4 (formerly the Submarine Department, and still secret), under the leadership of B.M. Malinin, managed the submarine construction works at the Baltic Shipyard. In subsequent years, 133 submarines were built to designs developed during Malinin's management. Additional developments included the formation of the Pacific Fleet in 1932 and the Northern Fleet in 1933. The forces were to be built around a core of powerful s. This building program was only in its initial stages by the time the German invasion forced its suspension in 1941. By the end of 1937, the biggest fleet was the Baltic Fleet based at Leningrad, with two battleships, one training cruiser, eight destroyers including one destroyer leader, five patrol ships, two minesweepers, and some more older minesweepers. The Black Sea Fleet at Sevastopol included one battleship, three cruisers, one training cruiser, five destroyers, two patrol ships, and four minesweepers. The Northern Fleet operating from the shores of Kola Bay and Polyarny was made up of three destroyers and three patrol ships, while the Pacific Fleet had two destroyers, transferred east in 1936, and six patrol ships assembled in the Far East. The Soviet Navy had some minor action in the Winter War against Finland in 1939–1940, on the Baltic Sea. It was limited mainly to cruisers and battleships fighting artillery duels with Finnish forts. World War II: The Great Patriotic War (1941–1945) Building a Soviet fleet was a national priority, but many senior officers were killed in Stalinist purges in the late 1930s. The naval share of the national armaments budget fell from 11.5% in 1941 to 6.6% in 1944. When Nazi Germany invaded in June 1941 and initially captured millions of soldiers, many sailors and naval guns were detached to reinforce the Red Army; these reassigned naval forces had especially significant roles on land in the battles for Odessa, Sevastopol, Stalingrad, Novorossiysk, Tuapse, and Leningrad. The Baltic fleet was blockaded in Leningrad and Kronstadt by minefields, but the submarines escaped. The surface fleet fought with the anti-aircraft defence of the