The post-World War II period represented the most dramatic territorial expansion in Soviet Ukraine's history, as the republic absorbed substantial territories from neighboring states, achieving an unprecedented geographical extent that would define its borders until independence.
The liberation and reconquest of Soviet territory during 1944 provided Moscow with the opportunity to redraw Eastern European boundaries fundamentally. Soviet Ukraine became the primary beneficiary of these territorial revisions, reclaiming lands lost in earlier conflicts and acquiring regions never previously under its control.
From Poland, Soviet Ukraine recuperated Western Ukraine, including the Volhynia and Galicia regions, which had been briefly incorporated following the Molotov-Ribbentrop Pact but subsequently occupied by Nazi Germany. The 1945 territorial settlement confirmed Soviet possession of these historically contentious areas, where Ukrainian populations predominated despite decades of Polish administration. This acquisition reunited the cultural heartland of Galicia, centered on Lviv, with the Soviet Ukrainian state, though the region's distinct historical experience under Habsburg and Polish rule created lasting cultural differences.
Romania's territorial losses to Soviet Ukraine were equally significant. Ukraine annexed Northern Bessarabia (Khotin region) and Southern Bessarabia, particularly the Budjak region along the Black Sea coast, restoring the Russian/Soviet access to the Danube River that had been lost in 1918. (The broader Bessarabian territory was primarily allocated to the newly created Moldavian Soviet Socialist Republic in 1940, which absorbed and effectively terminated the Moldavian Autonomous Soviet Socialist Republic that had existed within Ukraine since 1924.) Additionally, Northern Bukovina, never previously part of any Russian or Ukrainian state entity, was incorporated based on its substantial Ukrainian population and strategic importance. The small but symbolically significant Romanian-speaking Hertza region was likewise transferred, completing Soviet Ukraine's southwestern expansion and establishing the new border with the reduced Romanian state.
The most substantial new acquisition came from Czechoslovakia in 1945, when Transcarpathia—known as Carpatho-Ruthenia or simply Ruthenia—was annexed following a dubious plebiscite. This mountainous region, with its Rusyn population culturally and linguistically related to Ukrainians, had never been part of the Russian Empire but had belonged to Hungary and interwar Czechoslovakia. Its incorporation extended Soviet Ukraine to the Carpathian watershed and established borders with Hungary and Czechoslovakia, making Ukraine a geographically central European territory.
Internal Soviet adjustments also occurred during this period. Certain small areas, including portions of the Starodub region with Ukrainian populations, were transferred from the Byelorussian SSR to Soviet Ukraine, rationalizing internal boundaries along more consistent ethnic lines.
These new borders, established through war and diplomatic pressure, created a Ukrainian republic that united most ethnically Ukrainian territories for the first time in modern history, though at the cost of substantial population transfers, ethnic cleansing, and the subjugation of populations with diverse historical experiences under centralized Soviet control.
