Why didn't the Allies declare war the Soviets?

The West saw Fascism, probably rightly so, as a far greater threat than communism. Germany and Italy were the aggressors in Europe. The Allies were willing to work with Stalin, although he was a brutal dictator, to defeat Hitler, whom they saw as a more imminent danger. Hence the famous quote by Churchill about having tea with "the devil".

Britain and France, in an attempt to prevent further aggression by Hitler, had established a treaty with Poland stating that if Hitler invaded Poland that Britain and France would declare war on Nazi Germany. And so, when the Germans invaded Poland in 1939, Britain and France declared war on Germany. But they did not yet know about the secret Molotov-Ribbentrop Pact between the Nazis and Soviets dividing up eastern Europe. But when the Red Army moved into Poland later in September, as you noted, the Allies did not declare war. Sure, they were not obligated to do so, but they still could have.

If they had, wouldn't that have set what was at the time an alliance of only the British and French empires against the two largest military powers in the world, led by equally bloodthirsty dictators with no regard for human life? That would have been a stupid move. In any case, the Allies had enough foresight to see that a Soviet-German "alliance" could not last forever, and that the Soviet Union was a natural ally against Nazi Germany, and would probably be the deciding factor in the war. If they remained neutral with Russia, it was only a matter of time before they could become allies.

Well, I'm actually pretty sure that in WW2 the USSR was an ally of the Allies. The USSR was the force that finally BEAT Germany.

Churchill was asked how he could have worked with the USSR knowing what was coming from them (and he did, in his later writings), and he essentially said that given the choice between Hitler and the devil, he'd have tea with the devil.

Germany and Russia were not allies in WW2.

A) The French and Soviets were allies in WWI under the Franco-Russian Alliance, and the British and French were allies under the Anglo-French Entente. Therefore, using the transitive property, the British and Russians were understood common allies. Perhaps this carried to WWII?

B) The Russians are a powerful enemy to have in war. History shows messing with Russia leads to a loss (Napoleon entering Russia, Hitler invading Russia, etc...). This is why the French, US, and English took the Russian demands into consideration post WWII. They didn't want to anger the Russians.

It's surprising enough that they declared war on Germany. Germany had already done several things that should have forced a war already - eg, occupying the Sudetenland. When the allies did declare war, the Germans were genuinely surprised.

If they were so hesitant about going about Germany, why would they want any more on their plates?

there grew to become into no on the spot danger to the West from Soviet Union even after it invaded Poland. in comparison to Nazi Germany, the Soviet Union ought to no longer rapidly threaten England, France, or perhaps u . s . a . of america. there grew to become into additionally the thought the Soviet Union must be an best buddy against Nazi Germany which proved to be genuine. endure in suggestions that maximum Germans have been killed no longer struggling with the British, French, or individuals, yet whilst they have been confronted by way of the Soviet Union.