The British went to war over Poland. They had guaranteed Poland's independence against any [read German] aggression. If one reads the history, you will note Britain gave Germany something like 12 hours to cease military operations and withdraw from Poland, after which time, if Germany did not, a state of war would exist between the two countries. Poland was the casus belli.
VDH is right and you missed the point. Why did Britain take the step of assuring Poland its independence? Precisely because of Germany's systematic violations of Versailles. Poland is where Britain drew the line in the sand "so to speak".
Had Germany not violated the treaty, Britain would not have felt the need to make that guarantee. As for Russia's participation, it was simply following Germany's lead and would not, at that time, have considered invading Poland independently.
I didn’t miss the point. VDH’s ASSUMPTION is probably correct. But the FACT is the British gave as their SOLE reason for going to war the German invasion of Poland. And if Hanson can [rightly] challenge Buchanan’s factual errors [as well as Buchanan’s asuumptions], I can feel free to point out his.