In 1940 and early 1941, Hungary, Romania, and Bulgaria all agreed to adhere to the Tripartite Pact and thus join the Axis. Hitler then pressured Yugoslavia to join as well. The Regent, Prince Paul, yielded to this pressure, and declared Yugoslavia's accession to the Pact on 25 March 1941. This move was highly unpopular with the Serb-dominated officer corps of the military and some segments of the public: a large part of the Serbian population, as well as liberals and Communists. Military officers (mainly Serbs) executed a coup d'état on 27 March 1941, and forced the Regent to resign, while King Peter II, though only 17, was declared of age. Upon hearing news of the coup in Yugoslavia, Hitler called his military advisers to Berlin on 27 March. On the same day as the coup he issued Führer Directive 25, which called for Yugoslavia to be treated as a hostile state. Hitler took the coup as a personal insult, and was so angered that he was determined, in his words, "to destroy Yugoslavia militarily and as a state" ("Jugoslawien militärisch und als Staatsgebilde zu zerschlagen"), and to do so "with pitiless harshness" and "without waiting for possible declarations of loyalty of the new government". Hungary had joined the Tripartite Pact on 20 November 1940. On 12 December it also concluded a treaty with the Kingdom of Yugoslavia calling for "permanent peace and eternal friendship". The Hungarian leadership was split after Germany's War Directive 25 was delivered on 27 March 1941. Regent Miklós Horthy and the military favoured taking part in the invasion of Yugoslavia and mobilized the following day. Prime Minister Pál Teleki sought to prevent German troops passing through Hungary and cited the peace treaty with Yugoslavia as an impediment to cooperation with the Germans. On 1 April Yugoslavia redesignated its Assault Command as the Chetnik Command, after the Serb guerrilla forces from World War I which had resisted the Central Powers. The command was intended to lead a guerrilla war should the country be occupied. Its headquarters was transferred from Novi Sad to Kraljevo in south-central Serbia on 1 April. On 2 April, the German ambassador having already been recalled for "talks", the remaining embassy staff were ordered to leave the capital and to warn the embassies of friendly nations to likewise evacuate. This sent the unmistakable message that Yugoslavia was about to be invaded.