On March 31, 1939, Chamberlain, humiliated by the collapse of his Munich agreement and Hitler's occupation of Prague, handed, unsolicited, a war guarantee to a Poland then led by a junta of colonels.
To understand the rashness, the sheer irrationality of this decision, one must understand the issue involved and Britain's situation in 1939.
First, the issue: The Polish-German quarrel was over a city, Danzig, most British leaders believed had been unjustly taken from Germany at the end of World War I and ought to be returned.
The German claim to Danzig was regarded as among the most just claims Germany had from what most agreed by then had been an unjust and vindictive Treaty of Versailles.
What did the people of Danzig themselves want? Writes Overy:
"In May 1933, shortly after Adolf Hitler came to power in Germany, Danzig's National Socialist Party won 38 out of the city's 72 assembly seats and formed the city government. ... By 1936 there was a virtual one-party system. ... The strongly nationalist German population agitated in 1939 to come ... back home to Germany."
In short, the Germans wanted their city back, and the Danzigers wanted to go home to Germany. And most British had no objection.
Yet Britain backed up Poland's refusal even to negotiate, and when that led to war, Britain declared war on Poland's behalf.
Why did Britain do it?
After all, the war guarantee was given in response to the destruction of Czechoslovakia, but the Polish colonels had themselves participated in that destruction and seized a slice of Czechoslovakia.
Second, despite the guarantee, Britain had no plans to come to Poland's aid. Third, Britain lacked the means to stop Germany. When Hitler bombed Warsaw, British bombers dropped leaflets on Germany.
If Britain had no ability to save Poland and no plans to save Poland, why encourage the Poles to fight by offering what the British knew was a worthless war guarantee? Why declare a European and world war for a country Britain could not save and a cause, Danzig, in which Britain did not believe, in an Eastern Europe where Britain had no vital interest?
Said British Foreign Secretary Lord Halifax, "(We must) throw all we can into the scales on the side of law as opposed to lawlessness in Europe."
And throw it all in they did. And what became of Poland?
At Tehran and Yalta, another prime minister, Winston Churchill, ceded Poland to Stalin's empire, in whose captivity she remained for a half-century.