USSR invasion of Poland, why didn't Britain/France declare war?

In 1939, while Germany invaded Poland, the USSR went in and invaded the Eastern side of Poland.

England and France were quick to declare war on Germany, how did they view Stalin’s invasion?

I’ve raised the same question numerous times. I never received a satisfactory answer, from academics or otherwise. The only answer I can come up with is simple real politics.

One reason is that the German’s invasion was a violation of several treaties and prior war avoiding treaties. OTOH no one, or hardly anyone, ever dreamed that the Soviet Union would do such a thing. One way to view it is that Germany was repeatedly warned not to cross a line and did so, while the USSR suddenly crossed a line and surprised everyone.

Having said all that, it is not like the Allies did nothing:

In 1939 the Soviet Union was expelled from the League of Nations because of the Invasion.

Within 2 months of the Polish Invasion Stalin went into Finland and Britain and France (already at War with Germany), debated sending troops to aid the Finns, and actually decided to do so a few days before a Soviet-Finnish peace was concluded in March 1940. They, and the United States, sent a great deal of monetary and military support to the Finns in thier war with the Soviets.

England and France must had some pact signed with Stalin also ,there is no other explanation.

There is another explanation, which is that Britain and France saw no way to wage war against the Soviet Union and/or reckoned that their ability to wage war against Germany (which was their bigger concern) would be impaired by a parallel war against the Soviets. How would declaring war on the Soviet Union have helped Britain and France in any way in September 1939?

I believe the Soviets declared that they were not technically invading Poland. Their explanation was that the nation of Poland had ceased to exist sometime after the German invasion on September 1 and their own crossing of the eastern border on September 17. So the Red Army was just occupying uncontrolled territory that no existing government owned.

Admittedly it was the thinnest of fig leaves and the United Kingdom and France were under no obligation to accept the Soviet claims. But if offered the western allies an opportunity to avoid a second war they had no desire to enter.

Another reason, perhaps implied more than stated, was that we hoped to lose two troublesome upstarts at a stroke: As long as Hitler and Stalin occupied themselves with each other, the rest of Europe and America could more easily maintain their status quo and not have to try and jumpstart dead economies to fight massive foreign wars.

Of course, when France fell and the UK was saved by the merest of chances, the West faced the end of complacency.

Except that at the time of the USSR’s invasion of Poland, Hitler and Stalin weren’t “occupied with each other”; to the contrary, they were busy signing public non-aggression pacts, with secret protocols to divvy up Eastern Europe between them. Then, when Nazi Germany did invade the Soviet Union, almost two years later, the West accepted Stalin as an ally and began shipping him massive amounts of aid.

England was in no position to sign any pact with anyone, not being a sovereign nation. Or declare war. The United Kingdom & Nothern Ireland, however, is a different matter.

It could have be easily argued by the Soviets that they were simply preventing further parts of Poland falling into German hands. It’s open to interpretation, but that’s war and politics for you.

I’ve wondered why Nazi Germany and the Soviet Union didn’t secretly agree to have the Soviet Union go in first. Then Hitler could have claimed that he was forced to counterinvade to protect Germany’s eastern border. Britain and France would have fumed, but with the eastern half of Poland occupied by the pariah Communist state, the Western powers probably wouldn’t have had sufficient cause to declare war on Germany. Hitler would have gotten his latest acquisition and the war would have been delayed another couple of years.

They also put forward the claim that they were acting to safeguard the rights and safety of now dangerously exposed Ukrainian and Belarusian minorities in eastern Poland.

  • Tamerlane

The way I heard it it wasn’t so much that UK/France declared war because of Poland, but that that was the line they had drawn. That at first they hadn’t worried about Hitler, but that when he invaded, I forget, the Sudetenland? they realised they had to stand up to him or it would be too late, so they declared treaties with Poland. And then Hitler didn’t believe them because they hadn’t done anything yet and went ahead.

If so, the question is “Why did they want to stop German aggresian but not USSRian?” and I’d guess it was just a more immediate threat: that Germany was closer, and the relative growth was faster, and definitely wanted to conquer Europe, whereas USSR might not. And that they could hardly fight both so had to choose one or the other as unpalatable as that might be.

In the case of Britain, the technical reason was that their guarantee to Poland was absolute only in the case of a German invasion.

The original guarantee made by the British government on 31 March 1939 had been confirmed by the Anglo-Polish Agreement of Mutual Assistance agreed on 25 August. By this the two governments agreed to assist each other against any aggression by ‘a European Power’. So far, so straightforward. The bummer from the Polish point of view was that the Agreement contained secret clauses specifying that ‘a European Power’ meant Germany and that the appropriate response to any other acts of aggression would be decided only after the event. The British government was therefore able to ignore the Soviet invasion for all the reasons others have already mentioned and still keep to the letter of the Agreement. The reason the British had inserted the clause in the first place was, of course, that they foresaw that the Soviet Union might exploit a German invasion to make their own gains in Poland, a possibility that the Nazi-Soviet Pact had made all the more likely. As for the Poles, they were not really in a position to turn down the British promise of some assistance, however useless that was likely to prove.

I believe that it had to do with the fact that Germany had invaded Poland , but had ceded portions of the Poland to the soviet union , in return for the non aggression pact that molotov and von ribbonthorp had signed

This is a guess ,but the red army pre 1939 , was not the same red army as the post 1945 one was. Russia was not highly rated by anyone. Having said that , they may have simply calculated that at some point Hitler would move on russia , thus bringing them into the war on the side of the Allies.


Actually, the Soviets didn’t “simply calculate” that the Nazis would attack them. They, and everyone else in the world, knew this for certain. The Nazis had made their ultimate goal known since Hitler published Mein Kampf .

The 1939 border between Poland and the USSR was a result of a settlement after the Civil War in 1920, during which the Polish regime of General Pilsudski had attacked the Soviet Union. Large sections of land populated by ethnic White Russians and Ukrainians were ceded to Poland. The desire to protect these people and to move the inevitable German/Soviet front as far to the west as possible were the reasons for the Soviet advance into Poland.

The attack against Finland was the result of failed negotiations in which the Soviets sought to exchange Finnish territory near Leningrad for Soviet land elsewhere on the Soviet-Finnish border. The heavily fortified Mannerheim line, built with German assistance, was only a few miles from Leningrad and the Mannerheim government had always been hostile to the Soviet Union. This was in spite of the fact that the Soviet government had granted Finland, which had been part of the Czarist Russian empire, independence after the revolution of 1917. The huge propaganda campaign in the West in 1940, which charged that the Soviets merely wished to subjugate Finland, simply made no strategic sense from either a military or political angle.

This two volume set is must reading for those who want to understand the circumstances which led up to the Second World War.

Real politic. A declaration of war not only wouldn’t have helped Britain and France, it wouldn’t have damaged Germany or the Soviets and it wouldn’t have helped Poland.

Poland was gone even before the Soviets invaded. Why make an enemy that you couldn’t get at? And as things developed it would have turned out really awkward to have declared war on the Soviets and then tried to help them when Germany invaded. Let’s see, we were Britain’s ally but we wanted to aid the Soviets in their war with Germany, but Britain was at war with the Soviets. I guess Britain and the Soviets would have had to sign a treaty of peace.

Better to let sleeping dogs lie and not declare an inconsequential war on the Soviets.

Sorry Galen, but I have to correct some errors…

First, the sticking point in the negotiations before the war was the fact that the Russians wanted to build a naval base on an island at the coast of Finland.
That would have seriously compromised our neutrality, and therefor wasn’t acceptable.
Stalin wasn’t too thrilled and started to increase his demands. That of couse meaned that the negotiations failed and he had to start a war to get what he wanted.

Second, Mannerheim line was hardly heavily fortified. It consisted of some 200 gun emplacements or MG positions, a bunch of tank barriers made of concrete blocks that wouldn’t have stopped a VW Beetle.
Funnily enough, the Mannerheim line gets most of it’s fame from the rumors about it’s strength circulating among the Soviets during the war. I guess it’s easier to accept taking heavy losses against heavily fortified defenses…

Third, there was no Mannerheim government before 1944. He became the president because of his leadership in the continuation war, after the previous president Ryti had to leave his office so that the Ribbentrop-treaty which denied Finland the possibility of signing a peace treaty with Russia would be voided.

Fourth, the government wasn’t hostile to Russians. There was just a deep distrust of anything Russian in Finland for several reasons, mainly the uneasy relationship with the pre-revolutio Russia, including several campaigns of oppression by them and secondly the failed communist uprising in 1918.

And yes, I guess the Soviets weren’t merely trying to subjugate the Finns, but that would have been the result if they’d won a complete military victory.

(Funny how every time I post it’s something about Finland. I guess I have to move to Cafe Society : :dubious: :confused: :smiley: )

Another misconception is that Leningrad was somehow threatened by the Mannerheim line. The Mannerheim line was after all a series of static defenses; it wasn’t going to lift itself of its foundations and invade the Soviet Union.

And I think “granted” is a generous term for how Finland gained its independance.

Or maybe even the United Kingdom of Great Britain and Northern Ireland if you want to be pendantic :confused:

Never try to be pedantic unless you can spell it properly. :smiley: