to break through to France and later Britain through various routes. Aircraft: PZL P.7, fighter PZL P.11, fighter PZL.23 Karaś, light bomber and reconnaissance aircraft PZL.37 Łoś, twin-engine medium bomber Lublin R-XIII, observation, close reconnaissance and army cooperation plane, RWD-14 Czapla, observation, close reconnaissance and army cooperation plane RWD-8, training and liaison aircraft Polish Navy The Polish Navy was a small fleet composed of destroyers and submarines. Most Polish surface units followed Operation Peking, leaving Polish ports on 20 August, evading German forces and escaping to the North Sea to join with the British Royal Navy. Submarine forces were participating in Operation Worek, with the goal of engaging and damaging German shipping in the Baltic Sea, but with much less success. Warships (in service during September 1939) Gryf, large minelayer, sunk by German bombers in Hel base Błyskawica, a destroyer, escaped to United Kingdom Wicher, a destroyer, sunk by German bombers in Hel base Grom, a destroyer, escaped to United Kingdom Burza, a destroyer, escaped to United Kingdom Orzeł, a submarine, escaped to United Kingdom Sęp, a submarine, interned in Sweden Wilk, a submarine, escaped to United Kingdom Ryś, a submarine, interned in Sweden Żbik, a submarine, interned in Sweden Mewa, Jaskółka, Rybitwa, Czajka, Żuraw, Czapla - 6 small minesweepers. ORP Mewa, Jaskółka and Czapla were sunk by German bombers near Hel and Oksywie, others have been captured and salvaged by Germans. Mazur, an artillery training ship - and old torpedoboat from First World War, sunk by German bombers in Hel Two gunboats In addition, many ships of the Polish Merchant Navy joined the British merchant fleet and took part in various convoys during the war. Soviet Union Nazi Germany and the Soviet Union had negotiated about the upcoming invasion of Poland prior to signing the Molotov-Ribbentrop pact. The Soviet Union had been promised half of Poland if they helped the Germans to conquer the country. In the event, the German invasion began on 1 September 1939 but the Soviet Union held back until 17 September. When the Soviets attacked, Polish forces were forming a bridgehead in south-eastern Poland where they intended to make a last stand against the Germans - and if overwhelmed, to cross the border into Romania and make their way to the west to continue the fight from there. The Soviet invasion of Poland not only wrecked this plan, but also forced the Polish government to