Operation Margarethe (Unternehmen Margarethe) was the occupation of Hungary by Nazi German forces during World War II, as it was ordered by Hitler on 12 March 1944. A plan for the occupation of Romania was devised under the name Operation Margarethe II but was never carried out.
Hungarian Prime Minister Miklós Kállay (in office from 1942), with the knowledge and approval of Regent Miklós Horthy, secretly sought to negotiate a separate peace with the Allies in early 1944. German dictator Adolf Hitler wanted to prevent the Hungarians from turning against Germany, as Hungary's oil was desperately needed for the war effort. On 12 March 1944, German troops received orders by Hitler to capture critical Hungarian facilities.
Hitler invited Horthy to the Palace of Klessheim, near of Salzburg, on 15 March. 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 minister Dietrich von Jagow who stated that Horthy had to see him immediately at the German legation. When Horthy arrived, Jagow gave him a letter from Hitler saying the Fuhrer wanted to see him at the Schloss Klessheim in Austria on 18 March. As the two heads of state conducted their negotiations at the Schloss Klessheim, German forces quietly marched from German-occupied Austria into Hungary. The meeting served merely as a German 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 occupation of Hungary began.
When Horthy arrived in Budapest, German soldiers were waiting for him at the station. Horthy was told by Jagow that Hungary could only remain sovereign if he removed Kállay in favor of a government that would cooperate fully with the Germans. Otherwise, Hungary would be subject to 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 immobilize the Hungarian army, but with Soviet forces advancing from the north and east, and with the prospect of British and American forces invading the Balkans, the German military decided to retain Hungarian forces in the field, sending a portion to defend the passes through the Carpathian Mountains against possible invasion.
As a consequence of the Nazi occupation, Adolf Eichmann arranged the transportation of 550,000 Hungarian Jews from wartime Hungary (including Jews from territories annexed from Czechoslovakia, Romania, and Yugoslavia) to the Nazi death camps, with the collaboration of Hungarian authorities.[need quotation to verify]
Operation Margarethe II was the name for a planned invasion of Romania by German forces in conjunction with those of Hungary if the Romanian government decided to surrender to the Soviet Union and to switch sides. Romania in fact switched sides in August 1944 after King Michael's Coup, but the operation was never implemented.