From The Rise and Fall of the Third Reich (William L. Shirer, 1960, 2011) p824-6
The coup in Belgrade threw Adolf Hitler into one of the wildest rages of his entire life. He took it as a personal affront and in his fury made sudden decisions which would prove utterly disastrous to the fortunes of the Third Reich.
He hurriedly summoned his military Chieftains to the Chancellery in Berlin on March 27 – the meeting was so hastily called that Brauchitsch, Halder and Ribbentrop arrived late – and raged about the revenge he would take on the Yugoslavs. The Belgrade coup, he said, had endangered both Marita and, even more, Barbarossa. He was therefore determined, “without waiting for possible declarations of loyalty of the new government, to destroy Yugoslavia militarily and as a nation. No diplomatic inquiries will be made,” he ordered, “and no ultimatums presented.” Yugoslavia, he added, would be crushed with “unmerciful harshness.” He ordered Goering then and there to “destroy Belgrade in attacks by waves,” with bombers operating from Hungarian air bases. He issued Directive No. 25 for the immediate invasion of Yugoslavia and told Keitel and Jodi to work out that very evening the military plans. He instructed Ribbentrop to advise Hungary, Rumania and Italy that they would all get a slice of Yugoslavia, which would be divided up among them, except for a small Croatian puppet state.
And then, according to an underlined passage in the top-secret OKW notes of the meeting, Hitler announced the most fateful decision of all. “The beginning of the Barbarossa operation,” he told his generals, “will have to be postponed up to four weeks.”
This postponement of the attack on Russia in order that the Nazi warlord might vent his personal spite against a small Balkan country which had dared to defy him was probably the most catastrophic single decision in Hitler’s career. It is hardly too much to say that by making it that March afternoon in the Chancellery in Berlin during a moment of convulsive rage he tossed away his last golden opportunity to win the war and to make of the Third Reich, which he had created with such stunning if barbarous genius, the greatest empire in German history and himself the master of Europe. Field Marshal von Brauchitsch, the Commander in Chief of the German Army, and General Halder, the gifted Chief of the General Staff, were to recall it with deep bitterness but also with more understanding of its consequences than they showed at the moment of its making, when later the deep snow and subzero temperatures of Russia hit them three or four weeks short of what they thought they needed for final victory. For ever afterward they and their fellow generals would blame that hasty, ill-advised decision of a vain and infuriated man for all the disasters that ensued.
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For this short-range objective, the Nazi warlord was again right in his prediction, but he seems to have had no inkling how costly his successful revenge on Yugoslavia would be in the long run. At dawn on April 6, his armies in overwhelming strength fell on Yugoslavia and Greece, smashing across the frontiers of Bulgaria, Hungary and Germany itself with all their armor and advancing rapidly against poorly armed defenders dazed by the usual preliminary bombing from the Luftwaffe.
Belgrade itself, as Hitler ordered, was razed to the ground. For three successive days and nights Goering’s bombers ranged over the little capital at rooftop level-for the city had no antiaircraft guns – killing 17,000 civilians, wounding many more and reducing the place to a mass of smoldering rubble. “Operation Punishment,” Hitler called it, and he obviously was satisfied that his commands had been so effectively carried out. The Yugoslavs, who had not had time to mobilize their tough little army and whose General Staff made the mistake of trying to defend the whole country, were overwhelmed. On April 13 German and Hungarian troops entered what was left of Belgrade and on the seventeenth the remnants of the Yugoslav Army, still twenty-eight divisions strong, surrendered at Sarajevo, the King and the Prime Minister escaping by plane to Greece.
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