諾門罕戰役
Poland had a million-man army, but fell far short in terms of leadership, training, and equipment. The Polish military budget was about 2% of Germany's; its commanding general, Marshal Smigly-Rydz was not well prepared for the challenge. The Soviet Red Army then invaded Poland without a formal declaration of war on 17 September 1939, immediately after the undeclared war between the Soviet Union and the Empire of Japan at the Battles of Khalkhin Gol (Nomonhan) in the Far East had ended. Poland was then partitioned between Germany and the Soviet Union.