Even when on September 1st, 1939, after the Soviet-German pact had been signed, shots resounded in the Free City of Danzig, the Western powers mustered up only enough courage to embark on the so-called phoney war. Their belief in being able to save their own skin by turning a blind eye on the destruction of Danzig emboldened Hitler to make the next act of aggression. After that he captured Warsaw, then another European capital, Paris, and not long after that the Nazis started dropping bombs on London. Only then the Allies cried out loud: “This must stop! Let’s win this war once and for all!”

http://www.economist.com/blogs/easternapproaches/2014/09/polands-intellectuals-appeal?fsrc=scn/tw/te/bl/ed/fromdanzigtodonetsk – 9/1/2014.