National Legionary State in the context of "Horia Sima"

Ion Antonescu (/ˌæntəˈnɛskuː/; Romanian: [iˈon antoˈnesku] ; 14 June [O.S. 2 June] 1882 – 1 June 1946) was a Romanian military officer and marshal who presided over two successive wartime dictatorships as Prime Minister and Conducător during most of World War II. Having been responsible for facilitating the Holocaust in Romania, he was overthrown in 1944, before being tried for war crimes and executed two years later in 1946.

A Romanian Army career officer who made his name during the 1907 peasants' revolt and the World War I Romanian campaign, the antisemitic Antonescu sympathized with far-right and fascist politics. He was a military attaché to France and later Chief of the General Staff, briefly serving as Defence Minister in the National Christian cabinet of Octavian Goga as well as the subsequent First Cristea cabinet, in which he also served as Air and Marine Minister. During the late 1930s, his political stance brought him into conflict with King Carol II and led to his detainment. Antonescu rose to political prominence during the political crisis of 1940, and established the National Legionary State, an uneasy partnership with Horia Sima of the Iron Guard. After entering Romania into an alliance with Nazi Germany, he eliminated the Guard during the Legionary Rebellion of 1941. In addition to being Prime Minister, he served as his own Foreign Minister and Defence Minister. Soon after Romania joined the Axis in Operation Barbarossa, recovering Bessarabia and Northern Bukovina, Antonescu also became Marshal of Romania.

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.

Between 21 and 23 January 1941, a rebellion of the Iron Guard paramilitary organization, whose members were known as Legionnaires, occurred in Bucharest, Romania. As their privileges were being gradually removed by the Conducător Ion Antonescu, the Legionnaires revolted. During the rebellion and subsequent pogrom, the Iron Guard killed 125 Jews, and 30 soldiers died in the confrontation with the rebels. Following this, the Iron Guard movement was banned and 9,000 of its members were imprisoned.