How did the Moldavian Soviet Socialist Republic form in 1940?

The formation of the Moldavian Soviet Socialist Republic (S.S.R.) in 1940 was a direct consequence of the German-Soviet Nonaggression Pact, which assigned Bessarabia to the Soviet sphere of influence.12

Following the collapse of the western European front in 1940, the Soviet Union issued an ultimatum to Romania in late June, demanding the cession of Bessarabia and northern Bukovina. Romania submitted, and Soviet troops occupied the region on June 28.1

In August 1940, the Moldavian S.S.R. was formally established by joining districts of central Bessarabia—inhabited primarily by Moldavians—with a portion of the existing autonomous Moldavian republic located across the Dniester. Chișinău was designated as the capital. Other territories, such as the Hotin district and the southern districts of Cetatea Albă and Izmail, were incorporated into the Ukrainian Soviet Socialist Republic. Following this formation, the Soviet authorities initiated land expropriation and the collectivization of agriculture.1