Hitler had an overriding ambition for territorial expansion, which was largely driven by his desire to reunify the German peoples and his pursuit of Lebensraum, “living space” that would enable Germans to become economically self-sufficient and militarily secure. Such goals were greeted with support by many within Germany who resented the harsh terms of the Treaty of Versailles, which had ended World War I. Through various means he was able to annex Austria and Czechoslovakia with little resistance in 1938–39. Then on September 1, 1939, Germany invaded Poland, which had been guaranteed French and British military support should such an event occur. Two days later both countries declared war on Germany, launching World War II.