establishment of the postwar Polish community in Britain. During the Second World War, most of the Poles arrived as military or political émigrés as a result of the combined German-Soviet occupation of Poland. As the invasion of Poland progressed throughout September 1939, the Polish government evacuated into Romania and from there to France. Based at first in Paris, it moved to Angers until June 1940, when France capitulated to the Germans. With the Fall of France, the Polish Government-in-Exile relocated to London, along with a first wave of at least 20,000 soldiers and airmen in 1940. It was recognized by all the Allied governments. Politically, it was a coalition of the Polish Peasant Party, the Polish Socialist Party, the Labour Party, and the National Party. Although these parties maintained only a vestigial existence in the circumstances of the war, the tasks of the Government-in-Exile were immense, requiring open lines of communication with, and control of, the Polish Underground State in situ and the Polish Underground Army in occupied Poland, and the maintenance of international diplomatic relations for the organization of regular Polish military forces in Allied states. On 4 July 1943 the Polish Prime Minister-in-Exile, General Wladyslaw Sikorski, who was also Commander-in-Chief of the Polish Armed Forces in the West, died in an air crash off Gibraltar as he was returning to Britain from an inspection tour of Polish forces in the Mediterranean theatre. Until the Germans' April 1943 discovery of mass graves of 28,000 executed Polish military reserve officers at Katyn, near Smolensk in Russia, Sikorski had wished to work with the Soviets. After Hitler's invasion of the Soviet Union in June 1941, the Soviets' importance to the Western alliance had grown while British support for Polish aspirations had begun to decline. As the war progressed, Polish plans to more completely incorporate Poland's underground Home Army into the broader strategy of the Western allies—including contingency plans to move Polish Air Force fighter squadrons, and the Polish Parachute Brigade, to Poland—foundered on British and American reluctance to antagonise a vital Soviet ally hostile to Polish autonomy; on the distance from British-controlled bases to occupied Poland, which lay at the extreme flying range of available aircraft; and on the frittering away of the Polish Parachute Brigade on a patently flawed British operation at Arnhem, the Netherlands. One of the most important Polish contributions to Allied victory had actually begun in late