Why did Great Britain not declare war on the Soviet Union when they invaded Poland in 1939?
Britain did indeed have an agreement with Poland that if she were invaded, we would come to their aid. When the Germans marched in, in cSeptember 1939, we declared war on Germany. The reason we did not declare war on Soviet Russia is because they have a much bigger army than we do and in any event, we believed then that the Soviet-German alliance would probably collapse quite quickly, which it did. The rest is history. The worst aspect of all of this is that firstly we did nothing really to help Poland and secondly, Britain was quite unprepared for war and did not want to get involved. As it turned out, we had very little choice.
