While all Romanian lands had fallen under Ottoman control during medieval times, the lands between the Prut River and the Dniester River fell under Russian control after the 1812 War, forming the Governorate of Bessarabia. The Kingdom of Romania gained its independence from the Ottoman Empire in 1878, and after the First World War and the Russian Revolution, the Eastern lands were once again reunited with Romania. By 1940, the Soviet Union reoccupied Bessarabia and the Northern half of Bucovina, as part of their agreement with Germany over spheres of influence in Eastern Europe. Meanwhile, Germany let their allies Hungary and Bulgaria annex other parts of the Romanian territory, greatly reducing the size of the Kingdom.
The German attack on the USSR in 1941 completely changed the dynamics. With German support, Romania reconquered Bessarabia and pushed East of the Dniester, occupying a vast area known as Transnistria that included the port and city of Odessa.
The German debacle starting in 1943 saw the Red Army push through Romania and reannex all lost territories, creating a new Soviet Republic of Moldavia in what was previously known as Bessarabia. As of 1991, this entity is an independent nation known as the Republic of Moldova.