The Kingdom of Romania, under the rule of King Carol II, initially maintained neutrality in World War II. However, fascist political forces, especially the Iron Guard, rose in popularity and power, urging an alliance with Nazi Germany and its allies. As the military fortunes of Romania's two main guarantors of territorial integrity—France and Britain—crumbled in the Battle of France, the government of Romania turned to Germany in hopes of a similar guarantee, unaware that Germany, in the supplementary protocol to the 1939 Molotov–Ribbentrop Pact, had already granted its permission to Soviet claims on Romanian territory.
In the summer of 1940, the USSR occupied Bessarabia and Northern Bukovina, severely weakening Romania and diminishing its international standing. Taking advantage of the situation, Hungary and Bulgaria both pressed territorial claims on Romania. The disputes, arbitrated by Germany and Italy, led to the further losses of Northern Transylvania and Southern Dobruja to Hungary and Bulgaria respectively. The popularity of the Romanian government plummeted, further reinforcing fascist and military factions, who eventually staged a coup in September 1940 that turned the country into a Legionary State under Mareșal Ion Antonescu in partnership with the Iron Guard. Romania officially joined the Axis powers on 23 November 1940. Antonescu assumed full control over Romania in January 1941 and invaded the Soviet Union with the Axis, providing equipment and oil to Germany and committing more troops to the Eastern Front than all other allies of Germany combined. Romanian forces played a large role during fighting in Ukraine, Bessarabia, and in the Battle of Stalingrad. Romanian troops were responsible for the persecution and massacre of 260,000 Jews in Romanian-controlled territories, though half of the Jews living in Romania survived the war. Romania controlled the third-largest Axis army in Europe and the fourth largest Axis army in the world.
