Sure - but the same “allies” that declared war against Germany for invading Poland in 1939 should have declared war against the Soviet Union (for the exact same reason) - and didn’t.
What a hoax...
Part of that is because the 1939 Anglo-Polish treaty specifically excluded Britain from defending Poland against Russian invasion. Another part is that the Polish-Russian border was still sort of fluid and the Poles were squabbling with the Russians about it.