No, Romania was never a part of the Soviet Union/USSR(Union of Soviet Socialist Republics).
At the end of WWII, Romania was occupied by the victorious Soviet Army, but the Soviets never fully annexed the country.
Instead of full annexation, the USSR opted to just change the political regime of the country.
And this is how Romania became a communist puppet state under the leadership of the Romanian Communist Party(known between 1948-1964 as the Romanian Workers’ Party), which was at that time more of a satellite party of the Soviet Union.
I. Romania before and during World War II
At the beginning of WWII, Romania decided to remain neutral. This situation would not last for long because of the territorial demands of the Soviet Union in 1940 and the later development of the war.
After losing some 30% of its pre-war territory to both the Soviet Union and the Axis coalition, Romania had to make a tough decision in order to survive.
As a result, Romania opted to join the Axis forces and after the start of Operation Barbarossa(June 22, 1941); it became one of the most important allies of Adolf Hitler on the Eastern Front.
Romania’s involvement in the war consisted mainly in supplying critical oil and grain supplies for the German economy and allowing the German troops to pass through its territory and use it as a base to attack the USSR.
In exchange, the German troops protected Romania against foreign aggression and during Operation Barbarossa the Wehrmacht supported the Romanian Army’s efforts to reclaim Bessarabia from the Soviet Union.
However, the luck of both Romania and the Axis was about to end during the years 1943-1944.
The involvement of Romania in the war on the Axis side would prove to be a costly decision.
After the Battle of Stalingrad, the Romanian Armies suffered huge casualties that were impossible to be replenished.
At the same time, the Allied Bombers targeted the critical oil infrastructure of the country and inflicted heavy damage, to both the economy and the civilian population.
In 1944, Romania’s luck would turn even worse with the approach of the Soviet Armies to its borders.
With the Romanian troops unable to stop the Soviet offensive, King Michael I and the remaining democratic leaders of the country orchestrated a coup against the pro-German/Axis government led by Ion Antonescu.
The coup took place on August 23, 1944, and it ended with the arrest of Ion Antonescu and its deposition.
In a matter of days, Romania switched sides and declared war on Nazi Germany, thus joining the cause of the Allied Nations.
Switching the sides also had an important side effect, the Soviet Armies entered Romania with virtually no opposition, with the exception of the Region of Transylvania which was still under German and Hungarian control.
II. Initial relations between Communist Romania and the USSR(1947-1964)
During this phase, the relations between Romania and the USSR cannot be explained without briefly presenting the broader political/ideological process known as Sovietization.
Sovietization in Romania in general followed the same steps as in many other Eastern European Countries.
1. Politically
With the help of the occupying Soviet Armies, the ranks of the Romanian Communist Party quickly grew and the once-obscure party of the interbellum time rapidly rose to the center of the political stage.
After the fraudulent elections of 1946, the Communist coalition, known as the “Bloc of Democratic Parties” gained an overwhelming majority in the Parliament.
The traditional parties(Liberal and Peasant) were purged and completely banned. Many of their former members were either arrested or executed.
With the Communist party now in control of a leftist coalition, the only obstacle was the socialist party.
But not for long, because on March 01, 1948, the Romanian Communist and Socialist party agreed to merge and form the Workers Party of Romania, which until the rise of Nicolae Ceausescu was the Single Allowed party in Romania.
The transition to a single-party dictatorship was thus completed.
2. Economically
Despite switching sides and actively participating in the war alongside the Soviet Army, Romania was treated as a defeated state during the Paris 1947, peace negotiations.
Its allied status in the final years of the war against Germany was not recognized. Furthermore, Romania was forced to pay a 300 million dollar debt for the war reparations. The Soviets would take advantage of this debt to economically exploit Romania.
The Soviet “tools” for the economical exploitation of Romania were known as Sovroms.
In theory, Sovroms were joint Soviet-Romanian economical enterprises, in which both the Romanians and the Soviets had to contribute with both capital and equipment.
The Sovroms were organized in many different sectors of the Romanian economy: from mining, construction, transport, and more…
In practice, the Soviets used the Sovroms to extort as many valuable resources and money from Romanian during its occupation time.
Under the cover of the Sovroms, the Soviets would steal 2 billion dollars worth of goods from Romania. For a better context, the Romanian GDP at the time was estimated only at 500 million dollars.
The end of Soviet dominance over the Romanian economy came after the death of Stalin.
The Romanian communists offered to acquire Soviet shares in the Sovroms.
The Soviets demanded 9 billion dollars for their shares, but after negotiations, the Romanians and Soviets agreed on 5 billion dollars which would be paid gradually until 1970.
3. Military
At the end of the war, in May 1945, the Soviet Army in Romania numbered approximately 80.000 soldiers, it then massively increased its numbers in just a few months, reaching 500.000 in November 1945, according to historians.
The real reason for the increased presence of Moscow’s troops, immediately after the end of the world conflagration, was the assurance of Soviet political dominance over Romania (like in other Eastern European countries).
The strength of the occupation forces of the Soviet Union in Romania reached a maximum in March 1946 (615.000 soldiers).
In 1947 it dropped between 60.000 and 130.000. But after the conclusion of the Paris Peace treaties of 1947, the Soviets reduced their military presence in Romania, to around 30.000 troops, in the last years of the stationing.
III. End of Soviet military occupation of Romania
So how did the Soviet Military occupation of Romania end? The entire chain of events is yet to be completely known because many documents from the Soviet archives are still secret.
From the Romanian side, some politicians and historians spread an interesting story, which is not documented.
According to this story, during a hunting party, and after many glasses of wine, Nikita Khrushchev was convinced by Gheorghe Gheorghiu Dej to sign a document with the agreement of the Soviet withdrawal from Romania.
A good story, but it is hard if not even impossible to accurately check it.
In reality, the withdrawal of the Soviets from Romania was more likely an initiative of the Kremlin, which was then simply agreed upon by the Communist leaders of Romania.
Coincidently, at the same exact time, Khrushchev wanted to reduce military spending to fund other projects. So the withdrawal from Romanian was seen as a win-win for both the Soviets and Romanians.
And thus in June of 1958, the remaining 30.000 Soviet soldiers started the preparations for the retreat from Communist Romania. The withdrawal of the Soviet army was completed in July of the same year.
The withdrawal of the Soviet occupation forces from Romania gave legitimacy and boosted the popularity of the Romanian Communist Leaders.
Gheorghe Gheorghiu Dej further exploited this moment by promoting its own version of communism, which would replace the Soviet-styled one, thus distancing even further from the policies of Moscow.
Gheorghiu Dej’s successor, Nicolae Ceausescu would further continue this course of action.
IV. Conclusion
Although Romania was under Soviet Military occupation for over 14 years, the country was never annexed by the Soviet Union. The main reason was that the Soviets were pleased only with the change of regime and economic exploitation through Sovroms and other means.
After the withdrawal of the Soviet armies in 1958, Romania took steps to distance itself from Moscow’s policies and attempted to forge its own path to socialism.
It is important here to note, that Communist Romania never completely cut all international relations with the USSR, and never existed the other international Communist organizations like the Warsaw Pact or Comecon, which were under Soviet control.
The ties with the USSR will only be cut after the victory of the Romanian Revolution of December 1989, which ended the total domination of the Romanian Communist Party in the country.