Passage: Following the Invasion of Poland in September 1939, German and Soviet troops divided the territory of Poland. Thus, Eastern Galicia and Volhynia with their Ukrainian population became part of Ukraine. For the first time in history, the nation was united.In 1940, the Soviets annexed Bessarabia and northern Bukovina. The Ukrainian SSR incorporated the northern and southern districts of Bessarabia, northern Bukovina, and the Hertsa region. But it ceded the western part of the Moldavian Autonomous Soviet Socialist Republic to the newly created Moldavian Soviet Socialist Republic. These territorial gains of the USSR were internationally recognized by the Paris peace treaties of 1947.

Question: when was the nation united first?
1940