The Soviet Union issues an ultimatum to Lithuania

The public non-aggression treaty included secret protocols dividing spheres of influence in Eastern Europe. It gave both governments room to pursue expansion and exposed smaller states to decisions...

After Germany invaded Poland, Soviet forces crossed the eastern border under the pact’s secret arrangements. Polish territory was divided between two occupying powers; residents faced arrests,...

Soviet forces crossed the Finnish border after failed negotiations over security near Leningrad. The war exposed the costs of Stalin’s coercive diplomacy and the Red Army’s weaknesses after the...

The Soviet Politburo approved a proposal to execute thousands of Polish officers and prisoners held by the NKVD. The killings at Katyn and other sites were part of a broader effort to eliminate Polish...

The treaty ended the Winter War and transferred Finnish territory, including the Karelian Isthmus, to the Soviet Union. Soviet security demands gained territory but at high military and diplomatic...

Elections held under occupation offered voters a single approved list and were followed by petitions for incorporation into the Soviet Union. These procedures supplied a veneer of popular consent...

The USSR’s Supreme Soviet accepted Lithuania as a union republic after occupation and controlled elections. Soviet rule brought land nationalization, arrests, deportations, and the dismantling of...

An agent linked to Soviet security killed Trotsky, who died the next day. The assassination removed Stalin’s most prominent revolutionary rival abroad and extended Soviet political violence beyond its...

The invasion opened a war of annihilation across Soviet territory. Stalin’s government had failed to prepare effectively despite warnings; civilians and soldiers endured occupation, mass killing,...

The emergency body concentrated wartime authority and coordinated the state, economy, and military. Soviet survival depended on the labor and sacrifice of diverse peoples, including workers, women,...