[VK538FY]

There is surely a lesson to be learnt from history. The UK offered certain assurances to Poland before WWII then backed off when it realised that the heat was too much.

[admissionsguy]

This has been debunked. The French and English did not intervene in force because Poland fell unexpectedly fast. If Ukraine had fallen in a matter of days, there also would not have been Western help.

[VK538FY]

Your focus is wrong. Poland made a number of political decisions based on British advice and promises. That the British and French couldn't lend a hand in time, is beside the point.

[hollerith]

In the UK's defense, 2 days after Germany's invasion of Poland, the UK declared war on Germany and started a blockade against Germany (which persisted till 1945). The next day, the UK bombed German warships in German harbors.