The resurgence of an independent independent Poland in 1918, briefly complicated by the Polish–Soviet War from 1918 to 1920, enabled the country to rapidly reorganise its polity, develop its economy, and resume its place in international forums. One of the Polish delegates at the Paris Peace Conference, was a London-based émigré, Count Leon Ostroróg. This two-decade period of advance was disrupted in September 1939 by a coordinated German and Soviet invasion that marked the beginning of World War II.