Wikipedia's animated map from Greater Romania
Transdniestria is a geopolitical fiction. The region was loosely defined as the region between the Dniester and Southern Bug river and was originally created by the Germans in WW 2 as a territorial sop to their Romanian allies. In 1940 Nazi Foreign Minister Ribbentrop pressured Romania to cede Northern Transylvania to Hungary in the Vienna Award. In an effort to placate the Romanians, the Nazis created the concept of Transdniestria as part of the invasion of the Soviet Union in June 1941, and awarded it to Romania, even though few ethnic Romanians lived there. The Romanians were allowed civil and military administration of the area until the Red Army approached in late 1943, and the Germans asserted military administration.
There is very little historical, ethnological, economic or geographical justification for the existence of “Transdniestria.” The only justification is as a part of Putin’s various regional political machinations.
Left over business from the breakup of the Soviet Union.
The Russian-speaking minority didn’t want to become part of Romania. When the Moldovan SSR government tried to outlaw Russian language and culture, to better intergrate with Romania, the Russian-speakers took offense to it.
A civil War soon started, and the commander of the local Soviet military garrison joined the Russian-speakers.
In the end, it took the Vice-President of Russia threatening to send in Russian forces before a Cease-fire and peace-keeping could be agreed on.
Wikipedia's animated map from Greater Romania