Hertza region
In 1939, the Soviet Union unsuccessfully attempted an invasion of Finland, subsequent to which the parties entered into an interim peace treaty granting the Soviet Union the eastern region of Karelia (10% of Finnish territory), and the Karelo-Finnish Soviet Socialist Republic was established by merging the ceded territories with the KASSR. After a June 1940 Soviet Ultimatum demanding Bessarabia, Bukovina, and the Hertza region from Romania, the Soviets entered these areas, Romania caved to Soviet demands and the Soviets occupied the territories.