In the intervening months, strenuous efforts had been made on the diplomatic front to secure the allegiance of the Balkan states. Hungary, Romania, and Slovakia had joined the Tripartite Pact in November 1940.106 Bulgaria, actively courted by Hitler since the previous autumn, finally committed itself to the Axis on 1 March.107 The last piece in the jigsaw was the hardest to fit in: Yugoslavia. Its geographical position alone made it vital to the success of an attack on Greece. Here, too, therefore, beginning in November, every attempt was made to bring about a formal commitment to the Tripartite Pact. The promise of the Aegean port of Salonika offered some temptation.108 The threat of German occupation — the stick, as always, alongside the carrot — provided for further concentration of minds. But it was plain that, among the people of Yugoslavia, allegiance to the Axis would not be a popular step. Hitler and Ribbentrop put Prince Paul under heavy pressure when he visited Berlin on 4 March. Despite the fear of internal unrest, which the Regent emphasized, Prince Paul’s visit paved the way for the eventual signing of the Tripartite Pact on 25 March. Hitler was prepared to accept the terms which the Yugoslav government stipulated: a guarantee of the country’s territorial integrity; no through-passage for German troops; no military support for the invasion of Greece; no future requests for military support; and backing for the claim to Salonika.109 But within hours of Prime Minister Cvetkovic and Foreign Minister Cincar-Markovic signing the Pact in Vienna, high-ranking Serbian officers, who had long resented Croat influence in the government, staged their coup.110
Hitler was given the news on the morning of the 27th. He was outraged. He summoned Keitel and Jodl straight away. He would never accept this, he shouted, waving the telegram from Belgrade. He had been betrayed in the most disgraceful fashion and would smash Yugoslavia whatever the new government promised.111 ‘The Führer does not let himself be messed around in these matters,’ noted Goebbels a day or two later.112 Hitler had also immediately sent for the heads of the Luftwaffe and army — Göring and Brauchitsch — together with Foreign Minister Ribbentrop. As usual putting a favourable complexion on unwelcome events, he now emphasized the good fortune that the coup had taken place when it had done, and not after ‘Barbarossa’ had already begun.113 As it was, there was still just about time to settle the Balkan issue.114 But there was now great urgency. Halder had also been peremptorily summoned from Zossen. Hitler asked him forthwith how long he needed to prepare an attack on Yugoslavia. Halder provided on the spot the rudiments of an invasion-plan, which he had devised in the car on the way from Zossen.115
By one o’clock, Hitler was addressing a sizeable gathering of officers from the army and Luftwaffe.116 ‘Führer is determined,’ ran the report of the Wehrmacht Operations Staff, ‘… to make all preparations to smash Yugoslavia militarily and as a state-form.’ Speed was of the essence. It was important to carry out the attack ‘with merciless harshness’ in a ‘lightning operation’. This would have the effect of deterring the Turks and offering advantages for the subsequent campaign against Greece. The Croats would back Germany and be rewarded with their autonomy. The Italians, Hungarians, and Bulgarians would have territorial gains at Yugoslavia’s expense in return for their support. The beginning of ‘Operation Barbarossa’, Hitler added, would have to be postponed for up to four weeks.117 There was no discussion.118 He ordered preparations to begin immediately. The army and Luftwaffe were to indicate their intended tactics by the evening.
Jodl summarized Hitler’s objectives in the military directive for the attack that went out the same day.119 The plans for the invasion of Greece and the build-up to ‘Barbarossa’ were fully revised at breakneck speed to allow for the preliminary assault on Yugoslavia. Hitler gave no sign of acknowledgement of the work of his General Staff.120 The operation was eventually scheduled to begin in the early hours of
