In 1939, the British and French empires were initially unwilling to honour even the letter of their solemn pledge to come to the aid of Poland if it was attacked.
And they remained in no mood to truly honour the spirit of that pledge and provide serious help to the Poles.
But - pushed by some bold MPs in the British Parliament - they at least (and at last) declared war on Hitler and thus began the formation of the coalition of people that finally stopped him.