German-Soviet Boundary and Friendship Treaty signed

Japanese and Mongolian forces clashed near the disputed frontier; Soviet forces intervened in support of Mongolia. The battle exposed competing imperial claims in East Asia and affirmed Mongolia’s...

The offensive encircled Japanese forces and decisively changed the balance on the border. It shaped Japanese strategic calculations and gave Georgy Zhukov prominence.

The pact publicly committed both states to non-aggression and included a secret protocol dividing spheres of influence in Eastern Europe. It enabled Germany to invade Poland without immediate Soviet...

The invasion began the European war. The Soviet-German pact’s secret arrangements shaped the partition of Polish territory, while civilians faced invasion, occupation, and displacement.

Soviet forces crossed the Polish border as the Polish state faced German invasion. Soviet authorities described the move as protecting Ukrainians and Belarusians, while it also extended Soviet control...

The agreement granted the USSR military bases in Latvia. Officially framed as mutual assistance, it constrained Latvian sovereignty and foreshadowed further Soviet pressure on the Baltic states.

The treaty transferred Vilnius to Lithuania but required Soviet military bases on Lithuanian territory. It combined a territorial concession with a powerful strategic foothold that compromised...

The Soviet government accused Finland of shelling Soviet positions and used the incident to intensify the crisis. Finland denied responsibility; the event became a pretext for terminating the...

Soviet forces crossed into Finland after negotiations over border security and territorial concessions failed. The invasion was an act of aggression that produced heavy civilian and military losses...

The League condemned the Soviet invasion of Finland and expelled the USSR. The decision exposed the weakness of collective security and the limits of Soviet claims to defend peace through...