In the event of any action which clearly threatened Polish independence and which the Polish Government accordingly considered it vital to resist with their national forces, His Majesty's Government would feel themselves bound at once to lend the Polish Government all support in their power. They have given the Polish Government an assurance to this effect. I may add that the French Government have authorized me to make it plain that they stand in the same position in this matter.
The turn of Poland had come.
William L. Shirer, The Rise and Fall of the Third Reich
. . . Chamberlain's change of heart did not stop at words. The next "small State" on Hitler's list was Poland. When the gravity of the decision and all those who had to be consulted are borne in mind, the period must have been busy. Within a fortnight (March 31) the Prime Minister said in Parliament:
I now have to inform the House that... in the event of any action which clearly threatened Polish independence and which the Polish Government accordingly considered it vital to resist with their national forces, His Majesty's Government would feel themselves bound at once to lend the Polish Government all support in their power. They have given the Polish Government an assurance to this effect.
I may add that the French Government have authorised me to make it plain that they stand in the same position in this matter as do His Majesty's Government. . . . [And later] The Dominions have been kept fully informed.
This was no time for recriminations about the past. The guarantee to Poland was supported by the leaders of all parties and groups in the House. "God helping, we can do no other," was what I said. At the point we had reached it was a necessary action. But no one who understood the situation could doubt that it meant in all human probability a major war, in which we should be involved.
Winston S. Churchill, The Gathering Storm
Sadly, they never did defend Poland.