Invasion of Yugoslavia

• 1. Coup And Directive No 25

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  On the morning of the 27th of March 1941, a group of Yugoslav military officers executed a coup d'état in Belgrade. They forced Regent Prince Paul to resign and declared seventeen-year-old King Peter II of age. This action overturned a government that had signed the Tripartite Pact with Germany just two days earlier on the 25th of March. The new leadership was dominated by Serb officers who viewed the pact as a betrayal of national interests. Within hours of the coup, Adolf Hitler received news of the change in Belgrade. He called his top military advisers to Berlin for an emergency meeting.

  Hitler issued Führer Directive No. 25 later that same day. The directive ordered the destruction of Yugoslavia as a state entity. It stated that the German army would act with pitiless harshness and without waiting for any declaration of loyalty from the new government. Hitler described the coup as a personal insult and vowed to destroy Yugoslavia militarily. The directive set the stage for a rapid invasion that began less than ten days later. The political landscape shifted overnight from tentative cooperation to open hostility between former allies.

• 2. Axis Deployment And Logistics

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  German forces prepared their attack from bases in three neighboring countries: Romania, Bulgaria, and Hungary. In Romania, over 170,639 German troops were stationed by January 1941. These units included the 12th Army and First Panzer Group, which assembled near Timișoara. They brought heavy bridging equipment to cross the Danube River. Romanian oil fields at Ploiești remained vital to the Nazi war effort throughout this buildup. German troops entered Bucharest on the 12th of October 1940 under the guise of training missions.

  Bulgaria served as another critical staging ground. By March 1941, the Luftwaffe had placed 355 aircraft there. Secret teams established fuel depots and air observation stations before official troop movements began. The 12th Army crossed the Danube into Bulgaria on the 28th of February 1941. Hungarian participation required complex negotiations. Prime Minister Pál Teleki committed suicide on the 3rd of April after being unable to prevent German transit through his country. Miklós Horthy eventually authorized mobilization of Hungarian forces on the 5th of April. The Hungarian Third Army would later advance into Bačka and Baranya regions.

• 3. Air War Over Belgrade

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  At 07:00 on the 6th of April 1941, the Luftwaffe opened its assault with Operation Retribution. Three hundred aircraft flew in relays from Austria and Romania to bomb the capital city. A quarter of these planes were Junkers Ju 87 Stuka dive-bombers protected by heavy fighter escorts. The initial raid occurred at fifteen-minute intervals across three distinct waves lasting twenty minutes each. For ninety minutes, a rain of bombs fell upon the center of Belgrade where government buildings stood.

  The bombing killed approximately four thousand inhabitants under the debris. Communication lines between the Yugoslav high command and field forces virtually disappeared overnight. Most general staff members escaped to suburban areas but lost control over their troops. The VVKJ deployed interceptors from six squadrons to attack each wave of bombers. Messerschmitt Bf 109E fighters and Hawker Hurricane Mk Is scored at least twenty kills among attacking bombers on that first day. Despite losing twenty fighters shot down and fifteen damaged, Yugoslav pilots continued desperate defense efforts throughout the morning hours.

• 4. Ground Offensive And Collapse

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  German armored columns crisscrossed Yugoslavia by the 11th of April while resistance remained concentrated around the capital. Four separate thrusts struck the Royal Yugoslav Army on the 10th of April. The XLI Panzer Corps advanced from Romania toward Belgrade. The XLVI Panzer Corps moved across the Slavonian plain from Austria. The LI Infantry Corps approached Zagreb from Austria. The XLIX Mountain Corps targeted Celje also from Austrian territory. By the end of that single day, units were retreating or surrendering across the entire country except along the Albanian frontier.

  A small German force led by Fritz Klingenberg entered central Belgrade on the 12th of April with only a handful of men. They bluffed about their size and threatened bombardment to force surrender. The city mayor capitulated at 18:45 hours that evening. Italian forces joined the ground offensive on the 11th of April moving toward Ljubljana and down the Dalmatian coast. Hungarian troops crossed into Bačka and Baranya regions the same day facing minimal resistance. King Peter II and his government fled the country on 14 and the 15th of April before being captured near Sarajevo.

• 5. Internal Schisms And Fifth Column

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  Infighting among Yugoslav citizens began even before Axis troops arrived in force. On the evening of 7, the 8th of April, Croats in the 108th Infantry Regiment rebelled near Grubišno Polje. They took command from Serb officers and were joined by elements of the 40th Auxiliary Regiment. The rebellious regiments entered Bjelovar where Mayor Julije Makanec proclaimed an Independent State of Croatia on the 8th of April. Vladko Maček and Ivan Šubašić sent messages urging units to maintain positions but these orders went unheeded.

  Scholars have proposed theories regarding ethnic divisions contributing to the speed of surrender. Some suggest fifth column activities by Croatians, Slovenians, and ethnic Germans played a significant role. Others argue this factor had little effect on the ultimate outcome. The main reason for collapse was that subordinate national groups including Slovenes and Croats refused to fight for a Serbian-dominated Yugoslavia. Defenses were built on the northern border when natural lines lay further south along rivers Sava and Drina. Only wholly Serbian units within Serbia itself offered effective opposition throughout the campaign.

• 6. Naval And Riverine Operations

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  The Royal Yugoslav Navy possessed three destroyers, two submarines, and ten motor torpedo boats as its most effective units at the start of the invasion. One destroyer named Ljubljana remained in dry dock while its anti-aircraft guns defended the fleet base at Kotor. Another destroyer Beograd was damaged by near misses from Italian aircraft off Šibenik after its starboard engine failed. It limped back to Kotor escorted by remaining forces for repairs.

  Four large river monitors patrolled the Danube, Drava, and Sava rivers. These vessels carried two 120 mm guns each plus smaller caliber weapons. On the 6th of April they shelled an airfield at Mohács in Hungary before withdrawing toward Novi Sad. Early morning attacks by German Ju 87 dive-bombers struck these monitors on the 12th of April. A bomb dropped straight down the funnel of the monitor Drava killed fifty-four crew members out of sixty-seven total. The remaining three monitors were scuttled by their crews later that day as enemy forces occupied bases and river systems. One destroyer Zagreb was blown up at Kotor by junior officers defying surrender terms.

• 7. Partition And Puppet States

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  An armistice signed on the 17th of April came into effect at noon on the 18th of April ending eleven days of fighting. The Kingdom of Yugoslavia was subsequently occupied and partitioned among Axis powers. Most of Serbia and Banat became a German zone of occupation while other areas were annexed by neighboring countries including Germany, Hungary, Italy, Albania, and Bulgaria. Croatia emerged as the Independent State of Croatia or NDH during the invasion period.

  This new puppet state comprised Srem, Bosnia and Herzegovina, and Croatian lands. Italian forces moved into Dalmatia from both northeastern Italy and Albanian-controlled territories after repelling initial Yugoslav attacks. Hungarian troops occupied only territories that had been part of Hungary before the Treaty of Trianon. Romania received six ex-Yugoslav aircraft captured by Germans as compensation for artillery support provided along the Danube border. Approximately two hundred thousand to three hundred forty-five thousand Yugoslav prisoners were taken excluding ethnic Germans and Hungarians who were quickly released after screening.