In 1940, Romania joined the Axis powers in order to gain protection from the Soviet Union. When Germany launched operation Barbarossa, a ground invasion of the USSR, 600,000 Romanian soldiers were fighting against the Russians. One of the larges battles of this initial invasion was when German and Romanian troops captured Sevastopol. However, the Romanian army would loose 110,000 soldiers. After this, Romania did not engage in as many battles against the Soviets but they did supply the Axis powers with oil. In 1944, a coup and the Soviet invasion of Romania resulted in a pro-Allied government being set up. As a result of this, Hungary and Germany would declare war on Romania (Romania was now part of the Allied powers). After joining the Allies, Romania and the Soviets would launch a siege of Budapest, resulting in Hungary's defeat. After the war, Romania became a part of the Soviet Union.