Why didn't we declare war on russia when the invaded Poland?

The invasion of Poland by the Soviet Union in 1939 was part of a secret protocol in the Molotov-Ribbentrop Pact, which divided Eastern Europe between Germany and the USSR. Western Allies, particularly Britain and France, were focused on countering Nazi Germany's aggression and were hesitant to engage in a conflict that could lead to a broader war. Additionally, the geopolitical landscape and military considerations at the time made direct confrontation with the USSR less feasible, leading to a more cautious approach. Ultimately, the focus was on containing the Nazi threat first before addressing the complexities of Soviet expansion.