However, the rapidly changing situation in Europe during 1940, as well as domestic political upheaval, undermined this stance.
As the military fortunes of Romania’s two main guarantors of territorial integrity—France and Britain—crumbled in the Fall of France, the government of Romania turned to Germany in hopes of a similar guarantee, unaware that the then dominant European power had already granted its consent to Soviet territorial claims in a secret protocol of 1939’s Molotov–Ribbentrop Pact.
In summer 1940 a series of territorial disputes were diplomatically resolved unfavorably to Romania, resulting in the loss of most of the territory gained in the wake of World War I. This caused the popularity of Romania’s government to plummet, further reinforcing the fascist and military factions, who eventually staged a coup that turned the country into a dictatorship under Mareșal Ion Antonescu.
As a member of the Axis, Romania joined the invasion of the Soviet Union on 22 June 1941, providing equipment and oil to Nazi Germany as well as committing more troops to the Eastern Front than all the other allies of Germany combined. Romanian forces played a large role during fighting in Ukraine, Bessarabia, Stalingrad and elsewhere. Romanian troops were responsible for the persecution and massacre of up to 260,000 Jews in Romanian-controlled territories, though most Jews living within Romania survived the harsh conditions.
According to historian and author Mark Axworthy, the second Axis army in Europe, arguably, belonged to Romania, though, this is disputed since many would agree that this position goes to the Italian army.
With popular support for Romania’s participation in the war faltering and German-Romanian fronts collapsing under the Soviet onslaught, King Michael of Romania led a coup d’état that deposed the Antonescu regime and put Romania on the side of the Allies for the remainder of the war; Antonescu was executed in June 1946.