In March 1944, Hungary was occupied by the Wehrmacht. This invasion was formally known as Operation Margarethe (Unternehmen Margarethe).^[1][2]

Hungarian Prime Minister Miklós Kállay, who had been in office from 1942, had the knowledge and the approval of Hungarian Regent Miklós Horthy to secretly seek negotiations for a separate peace with the Allies in early 1944. Hitler wanted to prevent the Hungarians from deserting Germany. On 12 March 1944, German troops received orders by Hitler to capture critical Hungarian facilities.^[3]

Hitler invited Horthy to the Palace of Klessheim, near Salzburg. On the evening of 15 March 1944, when Admiral Horthy was watching a performance of the opera Petofi, he received an urgent message from the German Embassy minister Dietrich von Jagow, which stated that he had to see Horthy immediately at the German legation.^[4] When Horthy arrived, von Jagow gave him a letter from Hitler saying Hitler wanted to see him at Schloss Klessheim in Austria on 18 March. As both heads of state conducted their negotiations at Schloss Klessheim, German forces not already stationed in Hungary quietly marched from Reichsgaue of the Ostmark into Hungary. The meeting served merely as a ruse to keep Horthy out of the country and to leave the Hungarian Army without orders.

Negotiations between Horthy and Hitler lasted until 18 March, when Horthy boarded a train to return home. On 19 March, the military occupation of Hungary began.

When Horthy arrived in Budapest, German soldiers were waiting for him at the station. Horthy was told by von Jagow that Hungary would remain sovereign only if he removed Kállay and replaced him with a government that would co-operate fully with Germany. Otherwise, Hungary would be subject to an undisguised occupation. Horthy appointed Döme Sztójay as prime minister to appease German concerns.

Being a complete surprise, the occupation was quick and bloodless. The initial German plan was to immobilise the Hungarian Army, but with Soviet forces advancing from the north and the east and the prospect of British and American forces invading the Balkans,^[5] the German military decided to retain Hungarian forces in the field and so sent troops to defend the passes through the Carpathian Mountains from a possible invasion.

Following the German military occupation, Adolf Eichmann was instructed to arrange the transportation of 550,000 Hungarian Jews from wartime Hungary (including Jews from territories that had been annexed from Czechoslovakia (Sub-Carpathian Ruthenia), Romania and Yugoslavia) to extermination camps with Hungarian authorities' collaboration.^[6]

Despite the occupation, Horthy regardless attempted to negotiate a peace treaty and surrender with the Soviet Union. By October 1944 the Soviet Budapest offensive was nearly ready to launch and Horthy made a radio broadcast that an armistice had been agreed. The Germans were ready, however. Horthy was overthrown in Operation Panzerfaust, a coup that placed the National Socialist-friendly Arrow Cross Party (NyKP) in power. Following the Siege of Budapest the capital fell to the Soviets on 13 February 1945 and the government fled.

• Hungary in World War II