Why do you think France and Britain declared war on Nazi Germany for invading Poland but not the USSR?

[Bat-Perv]

Politics and strategy i suppose. Neither Britain or France wanted war with the soviet union at that time and Britain strategically was looking at the soviet union as a potential future ally against the nazis.
When Russia invaded Poland it was the last nail in the coffin that finished Poland. Poland did a lot better in 1939 against the nazis than the French did.
On paper France was the most powerful land army in the world but was not ready for war in 1930 and like Britain came to fight a 1918 war in 1939. Russia was the 2nd most powerful on paper. The US believe it or not as militaries go was likd no10.
Russia also invaded Latvia, Lithuania, Estonia and Finland and the Britain considered going to war with Russia over this but saner more pragmatic thoughts prevailed
If Britain had declared war on Russia in 1939 they would have lost ww2. Remember the nazis swept aside the french with ease and British were pushed out Norway, pushed out of Belgium, pushed out of France, pushed out of Greece, crete, Latvia etc and the battle of the Atlantic raged, the sea war in the Mediterranean was vital then you've got to consider British territory in the middle east central asia and India which were vulnerable and the British would not be able to hold back armies of t34s which was the best Tank in the world at the time.
Why didn't Britain declare War on Russia after the surrender of Germany & Japan over the soviet annexation of Poland and Eastern Europe? Because they did not have the power to kick them out.

[Guffrus]

Thats not really the right question because the answer is so obvious.

We had already seen a generation of young men wiped out, no one wanted any war so its absurd to think that we would goto war with one of our allies having only just barely survived the fight with the Germans.

The real question, for me at least, is why did we buy the food the Russians stole from the Ukraine?

We knew it was happening at the time, we knew they were being starving to death.

Now maybe the average man in the street didn't know where that food was coming from, but some one did.

[JuliaStyles]

Because at the time they had an agreement to be allies with Germany until Germany stabbed them in the back and invaded them too.

[JPrez]

I think they saw Hitler as the bigger threat and felt that Stalin might be somewhat reasonable to work with. Also, if the enemy of your enemy can become your friend, you have a greater chance of defeating your enemy. Also, they were still unsure of how things would play out with the U. S. so they needed an ally with a significant military since there’s alone would probably not defeat Hitler.

[genericname85]

because germany and russia had a non aggression pact at the time. besides that, Russia had aggreed to basically "share" poland. half for germany, half for russia. so russia didn't declare war, cause they benefited from it.

https://en.wikipedia.org/wiki/Molotov%E2%80%93Ribbentrop_Pact

[Gedaria]

It was that it was Poland. It was that they had broken the regulation that ended the first world war. By entering Poland they were back at war.
Russia was a alley of Germany. To start with but went with the Western powers..

[Alexandrubaschet08]

Because they are a nation of pu**y and cowers whit no honor. That is the only reason. UK and France have all the power back then to take down Russia whit zero efort.

[Lionman95]

Because whereas Nazi Germany France and Germany had an alliance with the UDSSR.

[disgustingweebtrash]

I think it's mostly because Germany was warned not to, but the allies did ignore a lot of the USSR's moves (bessarabia, baltics, winter war and ofc the partition of poland)