First shots were fired yet before the midnight on 5 April 1941: German assault groups attacked several object along the Yugoslav borders. At 2:00 a German engineer group took by surprise the Yugoslav side of the Iron Gate and voided the Yugoslav plan to block the shipping on the Danube. At 5:00 German and Italian air forces set off for the action, and at 5:15 started the German attack on Skopje, Veles and Strumica. At 6:30 first aircraft from the German 4th Air Fleet flew over Belgrade.
The raid on Belgrade was conducted in several waves. The weak anti-aircraft artillery fought gallantly until it was overwhelmed. Pilots from the Yugoslav 5th Fighter Regiment, which possessed German planes Messerschmitt Bf-109, also fought gallantly and shot down 10 German machines, but due to the invaders’ superiority they lost 15 planes. It could not save the city bombed by several hundred of aircraft. Entire city quarters were levelled. The gas and electricity supplies were interrupted. At least 20,000 inhabitants died, many more were wounded.The German air forces repeated air raids on the city at the night of 7 April and on 7 and 8 April. Those raids disorganized the work of the Yugoslav administration, which under bombs was leaving in hurry to the places designated by the defence plans. It was not until 21:00 that the government gathered in Uzice to proclaim the general mobilization and to agree upon the appeal to the nation. That appeal though could not be broadcast, because the radio-station in Belgrade was destroyed.
The Supreme Command started its mobilization in the morning in Belgrade and it was not until 15:00 that it reached Banja Kovilaca, from where it attempted to contact subordinated units. Unfortunately, the command’s own signals battalion was not completely mobilized yet, and could not provide a fully operational service. Through the attaché in Athens there was sent an appeal to Gen. Aléxandros Papagos to start an offensive in Albania, and to Gen. Henry Maitland Wilson to start operations in the valley of Strumica.
In Athens it was estimated yet before the midnight that the German aggression was just a matter of hours, and the supreme command readied the troops concentrated on the Bulgarian frontier. At 5:00 the German ambassador, Viktor von Erbach zu Schönberg, demanded an immediate audience from prime-minister Aléxandros Koryzis. The prime-minister understood very well what the Prussian aristocrat in Nazi service was going to bring. He let the German wait 30 minutes, and meanwhile notified the king and the supreme commander. As soon as von Erbach was received, he started reading the note, but Koryzis interrupted saying that Greece would fight. At 6:00 the radio-station in Athens interrupted broadcasting the Sunday religious service, and announced the official communiqué about the German aggression, as well as the king and prime-minister’s declaration. The people’s reaction though this time was different than on 28 October 1940. They realized that it was too difficult for Greece to fight and to stand another mighty power.
The basic military events of the first, decisive stage of the war took place in south-east Yugoslavia, which played the key role to both sides. Holding there, combined with an offensive in Albania, would influence realization of the Yugoslav defence plan, which foresaw a possibility to retreat towarts the Greek border. To the Greeks it also created possibility to win time till the full concentration of the British Expeditionary Corps; the corps would be then used to support the troops fighting in the first line, or cover their retreat to a new defence position. To the invaders occupation of that area meant separation of the Yugoslav and Greek forces, removing the menace of an Italian defeat in Albania, and creation of the basis for the offensive against Greece along a broad front. So both sides concentrated in that area substantial forces. But the German 12th Army was fully prepared for combat, while the Allies lacked co-ordination and uniform command, and operated in several groupings.
Against south-east Yugoslavia from Bulgaria struck the core of the 12th Army. It focused its effort on three routes leading to Skopje, Veles, and Strumica. Meanwhile the Yugoslav units from the 3rd Army District fought along a wide defence front counting on favourable terrain conditions. But the German assault grouping already on the first day overcame the units detached from Yugoslav divisions to the border defence, and on 7 April their forces took Skopje, Veles and Strumica. The Yugoslav defence became disorganized. Attempts to organize defence on new positions failed due to collapse of the army. Within next three days the Germans met the Italians on the lake Ohrid, and broke the Greek defence in the vicinity of Salonika.
The left wing of the advancing German 12th Army, from the very moment it crossed the Greek border, encountered a stubborn defence of the Army Eastern Macedonia deployed on the system of permanent fortifications. Greek forts’ crews, supported by field units, as a rule used to let the enemies to approach at close distance in order to destroy them with well-organized fire. The strength of such organized defence made the Germans an unpleasant surprise. In most of the sectors their advance stalled and split into a series of fights for individual forts, especially in the areas of Nevrokopion and the Rupel pass. Only on the left wing of the Greek forces in the Kerkini (Bjelasnica) mountains the Germans mounted a substantial superiority in numbers and drove the Greeks to the rear position at Krusia. The overall situation though was determined by the events, which took place in the area of Strumica. Already in the evening of 7 April the command of the Army Eastern Macedonia received from there alarming news about the enemy successes, and on 8 April from there struck the enemy 2nd Armoured Division.
It rolled the Greek rear troops, and before evening reached Salonika. This way it cut the Army Eastern Macedonia’s land communications with the rest of the country. Its evacuation by sea was out of question due to lack of ships and the German superiority in the air. In those circumstances the commander of the army, Gen. Konstantinos Bakopoulos, capitulated.
The events on the Bulgarian frontier also decided about the fate of the joint Greco-Yugoslav offensive against the Italians in Albania. The Yugoslav 3rd Army, despite of its weakness, on 7 April undertook offensive operations in the vicinity of the lakes Shkodra in the north and Ohrid in the south, where it co-operated with the Greek Army Western Macedonia. Yet the Germans got to the Yugoslav rears and paralysed the Greco-Yugoslav operation. Only in the northern Albania the Yugoslavs achieved some local successes in the vicinity of Shkodra. Meanwhile on the other sectors of the borders with Bulgaria, Romania, Hungary, Germany and Italy everything was quiet yet – both sides were still concentrating their forces. Only on the Sava German motorized troops seized bridgeheads. The Yugoslav 4th Army counter-attacked to liquidate them, but without a success.
On 8 April the situation rapidly changed: along the axis Sofia – Belgrade struck the German 1st Armoured Group commanded by Gen. Ewald von Kleist. Already on the first day of the advance it broke the defence of the Yugoslav 5th Army and took Pirot. Next day the 11th Armoured Division developed the success and seized Nis, Aleksinac, and reached Rozanj. This strike cut the 5th Army in halves, which became isolated in the mountains. The road to Belgrade was open. In this situation the Yugoslav command decided to move the 6th Army from the Romanian frontier to the eastern bank of Morava in order to create a new defence position along the line Rudnik Mountains – Arandjelovac – Mladenovac – Grocka. The 11th Division meanwhile continued its advance and wedged into the zone of the Yugoslav concentration. On 10 April it took Paracin, Cuprija, Jagodina, and approached Markovec, where it encountered a stout defence of the 18th Infantry Regiment. Those were already Belgrade’s far approaches. Individual Yugoslav units fought gallantly, but without anti-tank and anti- air defence they inevitably had to succumb to the enemy’s joint air and armoured strikes.
Civilians were surprised by the swift pace of the campaign, but everywhere, where time and means permitted, were formed volunteer units to support fighting troops. The Germans in Yugoslavia had to take many towns in heavy street fights. However, there was no power to organize that spontaneous impulse while the army was too disorganized to use that help. One German soldier noted in his diaries:
All the hamlets along on the road to Kragujewatz are simultaneously the reminiscences of hard fights. Aleksinatz, Tschuprija, Jagodina… There was an officers school in Jagodina. The cadets had delivered a stubborn defence. (…) They fought to the last man.
When the Germans approached Kragujevac, defences were hastily built and anti-air guns were placed to fire at blank point. The manager of a local factory summoned his workers and said: Germans are coming. We should show them the traditional Serbian courage. But armed workers could not do much against the tanks. Nevertheless, they conducted precise fire at motorcyclists and infantry. Even eight days after taking Kragujevac by the Germans, fights still lasted there, and the Germans had losses in killed and wounded. In retaliation they shot 7000 city’s inhabitants.
A dangerous crisis meanwhile mounted in western Yugoslavia. In view of the successful advance of the 12th Army as well as internal situation in Yugoslavia the supreme command ordered the 2nd Army to start its advance on Sarajevo without waiting for the units, which were still in the process of concentration. The operation started on 10 April and from the beginning it assumed unexpected dimensions. The German advance became the signal for the fascist elements to raise their heads. The Yugoslav 4th Army, where served a lot of pro-fascist Croats, just disappeared and so the German advanced troops at 19:30 without a trouble entered Zagreb. There, according to a secret agreement concluded yet before the war, the leader of the local ustaši, Col. Slavko Kvaternik, broadcast by the radio the proclamation of so-called Independent State of Croatia (NDH). He called upon the Croats, especially soldiers, to plead allegiance to NDH. Then was broadcast the statement of Dr. Vlatko Maèek (still the deputy prime-minister in the government of Dušan Simoviæ), which supported the declaration of creation of the NDH. Those appeals activized fascist and capitulationist elements in Croatia. They started to take over the administration and demoralize units, where most of the soldiers were the Croats. They ceased fighting with the Germans, and in many cases also disarmed the soldiers of the Serbian nationality.
The events in Croatia isolated Slovenia from the rest of the country. There too fascists and capitulationists declared severance with Belgrade and tried to contact the Germans. The 7th Army, formed mostly of the Slovenes, ceased to exist as a combat unit under the orders of the supreme command.
It was not until 10 April that the Yugoslav Supreme Command, which so far estimated the situation rather optimistically, saw the signs of catastrophe. The orders were issued to all the units to fight without waiting for direct orders from above. Simultaneously it was decided to organize the defence farther in the hinterland and around Belgrade. They counted on the 6th Army’s ability to regroup and halt the enemy advancing from Sofia, and on the 1st and 2nd Armies, which had to withdraw from Bachka and Baranya and strengthen the defence in the south.
The orders though were issued too late. The whole armies cased to exist. On 10 and 11 April German forces, now also actively supported by Hungarian and Italian troops, were running ahead. The centre of gravity of their operations was now Belgrade, to which from the south-east was approaching the 1st Armoured Group with the 11th Armoured Division in front; from the west was advancing the XLVI Corps, and from the nearby Banate – the XLI Corps. The Yugoslavs had a lot of troops around Belgrade, but they were disorganized and without a proper command. On 11 April the 11th Division overcame the 18th Infantry Regiment and took Topola by surprise. Two days later the same division took Ralje.
In those circumstances the commander of the Yugoslav 6th Army decided that a defence of Belgrade would be pointless and ordered withdrawal of his troops to the left bank of the river Topcider. On 12 April at 17:00 the XLI Corps without fights entered into the city, and on the next day the 11th Division reached it from the south-east, and the 8th Infantry Division from the XLVI Corps from the west. The advance of the XLVI Corps driven from the west to the east in between Sava and Drava rivers menaced the flanks and the rears of the retreating 1st and 2nd Armies. The 2nd Army dispersed without a battle, and in the 1st Army only few units managed to get to the southern bank of Sava. Yet the border and fortress units were still holding their positions. Against them on 11 April struck the Hungarian 2nd Army, which after several clashes occupied Bachka and Baranya.
Menwhile ustaši were seizing power in almost whole Croatia. The Germans without a trouble reached Banja Luka, and the Italian 2nd Army entered Ljubljana and met the Germans at Karlovac. The German 2nd Army was developing its advance on Sarajevo. On 13 April the Yugoslav army was practically defeated, although some troops kept fighting. In this situation gen. Simoviæ, while remaining the prime-minister, handed the duties of the chief of staff of the supreme command over to Gen. Danilo Kalafatoviæ, and authorized him to enter negotiations with the Germans concerning a ceasefire. He expected that it would be possible to obtain conditions similar to those, which were granted to France. Gen. Kalafatoviæ assumed his new duties on 14 April at 9:00 and immediately undertook preparations for ceasefire. At 9:30 the supreme command issued the defeatist directive No.179, which played the same role as Pétain’s appeal of 17 June 1940:
In result of defeat on all the fronts, in result of a complete disintegration of our troops in Croatia, Dalmatia and Slovenia, and after a comprehensive examination of our political and military situation we have come to the conclusion, that any further resistance is impossible and may only bring about the unnecessary bloodshed, without any prospect of a success; furthermore as neither our nation nor its military leadership wanted the war, we have resolved (…) to ask the German and Italian commands to cease the hostilities.
In the evening Kalafatoviæ sent his plenipotentiary envoys to the command of the German 2nd Army to undergo ceasefire talks. But on the same day Adolf Hitler, obsessed with the idea of destruction of Yugoslavia as a country, demended an unconditional capitulation. Until then the military operations had to be continued. On 15 April Berlin and Rome recognized the Independent State of Croatia. Also north-eastern parts of Slovenia, so-called Lower Styria and Upper Carinthia, were subordinated to the German administration. Thus started the partitions of Yugoslavia. On the same day the Bulgarian Telegraph Agency issued the following statement:
Today the government of Bulgaria severed diplomatic relations with Yugoslavia. In the note presented to the Yugoslav envoy it has been stated, that such a decision was influenced by following reasons:
Assaults, which the troops of the Yugoslav forces have committed without a reason since the beginning of the current month.
Assaults from the air of the Yugoslav aviation on Bulgarian cities, during which killed were civilians – especially women and children – although Bulgaria was aside the conflict.
The main reason however is that the members of the Yugoslav legation in Sofia maintained contacts with subversive elements, which were preparing riots and a coup d’état.
On 15 April, in result of the partial ceasefire agreement with the commander of the XXXVI Army Corps, the Yugoslav command ordered the commanders of the 2nd Army Group and the 4th Army to cease hostilities. The ceasefire was in effect in the west of the road Zvornik – Sarajevo. Th troops were ordered not to resist the Germans, but not to lay their arms down either. In result in the whole Bosia, north to the line Visegrad – Sarajevo – Bugojno ceased any resistance.
In the afternoon the Yugoslav government held the last conference on the native soil in Niksic. It was resolved that Yugoslavia would not capitulate as a state, but only the armed forces would sign the act of surrender. The king and the govenment had to go to Greece to continue the war abroad; they flew to Greece the same night. The deputy prime-minister Slobodan Jovanoviæ explained it as follows:
If the army capitulates, then Yugoslavia as a state will have no liabilities before the winners. Contrary, if we capitulate as a country, as a state, and the government confirms the capitulation, then this way we will deem ourselves vanquished, and the country and the state will assume certain liabilities before the winners.
On 17 April in the morning a Yugoslav delegation with Dr. Aleksandar Cincar-Markoviæ and Gen Radivoje Jankoviæ in van was trnsported by a German bomber from Sarajevo to Zemun. At 20:00 they were received in the building of the former Czechoslovak embassy in Belgrade by the commander of the German 2nd Army, Gen. Maximilian von Weichs. He announced to the Yugoslav delegation, that Yugoslavia had been defeated, and called upon the delegation to sign the act of unconditional capitulation. They were given half an hour to make any formal remarks concerning the presented text.
The document stated that the Yugoslav armed forces unconditionally capitulated and surrendered. For that the troops had to gather in their respective units, and until the arrival of the Germans the Yugoslav officers were responsible for the order and discipline. Soldiers, who after the surrender left their units would be punished by death. All the weapon and equipment, as well as the archives of the prime- minister, foreign office, army, and navy had to be handed over to the Germans. Soldiers were forbidden to leave the country. It was a brutal dictate, humiliating in its form and contents. The Yugoslav delegation had no choice but to sign it. They did it at 21:00. The ceasefire was in effect since next day, 18 April at 12:00.
On 17 April during a conference in Athens the Yugoslav government issued an appeal to the nation, which stated that Yugoslavia was still in war and would continue the struggle alongside the Allies until the final victory. Meanwhile in Yugoslavia the German, Italian and Hungarian troops began the occupation of the country. On 19 April Bulgarian troops entered into southern Yugoslavia. The rests of the Yugoslav army surrendered or dispersed. On 24 April at 12:00 ceased its existence the Yugoslav Supreme Command. As many as 375,000 soldiers marched into captivity. Some non-Serbs were soon released, so effectively about 200,000 soldiers (90% Serbs) remained prisoners of war.