Most people in the West tend to think of Operation Barbarossa as a purely German military campaign against the Soviet Union.

That picture, though, is far from complete. Nazi Germany didn't go it alone — five other nations joined the assault, which helps explain how the invading force mustered a frontline strength of 3.8 million, dwarfing the Soviet Union's estimated 2.6 to 2.9 million troops on the front lines. Among those allied nations was Romania, which threw its support behind the operation in return for territorial gains, including the region of Transnistria.

Romania had emerged from World War I on the winning side, and the spoils were considerable. The collapse of both the Austro-Hungarian Empire and the Russian Empire opened the door for Romania to absorb Bessarabia, Bukovina and Transylvania. With these additions, the country realized its long-held ambition of uniting all ethnic Romanians under a single nation-state. Yet this came with a significant downside: the incorporation of large ethnic minority populations, planting the seeds of future conflicts.

When World War II erupted, Romania initially chose neutrality. But as its guarantors Great Britain and France saw their fortunes decline, the country found itself squeezed between the competing demands of Germany and the Soviet Union. One by one, Romania surrendered most of its newly acquired territories without resistance. The resulting backlash destroyed King Carol II's base of support, paving the way for a pro-German fascist regime to seize power.

So when Germany unleashed Operation Barbarossa, Romanian troops marched alongside their German counterparts.

The payoff was swift. Romania took back both Bessarabia and northern Bukovina, which had previously been handed over to the Soviet Union. Beyond that, on August 19 of 1941, it asserted control over Transnistria — the territory stretching between the Dniester and Southern Bug — for the first time. This new acquisition was intended to offset the painful loss of northern Transylvania, which Romania had been compelled to cede to Hungary under German pressure.

Romania's grip on the territory proved short-lived, lasting only until early 1944, when the Soviet Union's westward advance through Eastern Europe swept it away.