This article details the order of battle of the Polish Navy prior to the outbreak of World War II and the Polish Defensive War of 1939. Following World War I, Poland's shoreline was relatively short and included no major seaports. In the 1920s and 1930s, such ports were built in Gdynia and Hel, and the Polish Navy underwent a modernisation program under the leadership of Counter-Admiral Józef Unrug (Commanding Officer of the Fleet) and Vice-Admiral Jerzy Świrski (Chief of Naval Staff). Ships were acquired from France, the Netherlands, and the United Kingdom, and the navy was to be able to secure the Polish supply lines in case of a war against the Soviet Union. By September 1939 the Polish Navy consisted of 5 submarines, 4 destroyers, and various support vessels and mine-warfare ships.