Peacetime organisation

According to regulations issued by the VKJ in 1935, the 38th Infantry Division Dravska (38th ID) was to be raised from the Dravska divisional district, which was headquartered in Ljubljana. The Dravska divisional district was under the control of the 4th Army district, headquartered in Zagreb. The division was named for the Drava river, which runs through the Styria region, and was largely manned by Slovene and ethnic German troops. In peacetime, the Dravska divisional district included:^[12]

• 37th Infantry Regiment, based in Ribnica
• 39th Infantry Regiment, based in Celje
• 40th Infantry Regiment, based in Ljubljana
• 45th Infantry Regiment, based in Maribor
• 16th Artillery Regiment, based in Ljubljana
• 32nd Artillery Regiment, based in Maribor

Wartime organisation

The wartime organisation of the VKJ was laid down by regulations issued in 1936–37,^[13] which set the strength of an infantry division at 26,000–27,000 men.^[5] A total of 11,200 horses and other pack and draught animals were required to provide mobility for each infantry division. The theoretical wartime organisation of a fully mobilised Yugoslav infantry division was:^[14][15]

• headquarters
• divisional infantry headquarters, with three or four infantry regiments
• divisional artillery headquarters, with one or two artillery regiments
• a cavalry battalion with two squadrons, a bicycle squadron and a machine gun platoon
• a pioneer battalion of three companies
• an anti-tank company, equipped with twelve 37 mm (1.5 in) or 47 mm (1.9 in) anti-tank guns
• a machine gun company
• an anti-aircraft machine gun company
• a signals company
• logistics units

Each infantry regiment was to consist of three to four infantry battalions and a machine gun company.^[16] The divisional artillery regiments were animal-drawn and largely equipped with World War I-vintage pieces.^[17] An artillery regiment consisted of four battalions, one of 100 mm (3.9 in) light howitzers, one of 65 mm (2.6 in) or 75 mm (3.0 in) mountain guns, and two of 75 mm (3.0 in) or 80 mm (3.1 in) field guns.^[18] The 37th, 39th and 40th Infantry Regiments and the 16th and 32nd Artillery Regiments, which were administered by the Dravska divisional district in peacetime, were earmarked to join other formations when they were mobilised, and the division was to be brought up to its wartime strength by the 38th and 112th Infantry Regiments and 38th Artillery Regiment from the VJK reserve.^[14][19]

Mobilisation

Following unrelenting political pressure from Adolf Hitler, Yugoslavia signed the Tripartite Pact on 25 March 1941. Two days later, a military coup d'état overthrew the government that had signed the pact, and a new government was formed under the Royal Yugoslav Army Air Force commander, Armijski đeneral^{[lower-alpha 2]} Dušan Simović.^[24] A general mobilisation was not called by the new government until 3 April 1941, out of fear of offending Hitler and thus precipitating war.^[25] This hesitation was in vain, for on the same day as the coup Hitler had issued Führer Directive 25 which called for Yugoslavia to be treated as a hostile state, and on 3 April, Führer Directive 26 was issued, detailing the plan of attack and command structure for the invasion, which was to commence on 6 April.^[26]

According to a post-war U.S. Army study, by the time the invasion began, the 38th ID had only commenced mobilising,^[27] and was largely in its mobilisation centres or moving to concentration areas. On 6 April, the elements of the division were located as follows:^[28][29]

• the divisional commander Divizijski đeneral^{[lower-alpha 3]} Čedomir Stanojlović, his chief of staff Major Ivan Babić, and their headquarters staff were mobilising in Slovenska Bistrica
• the divisional infantry headquarters and 45th Infantry Regiment were mobilising around Maribor
• the 38th Infantry Regiment was mobilising in Maribor, Slovenska Bistrica and Ptuj
• the 112th Infantry Regiment (less its 1st Battalion) was marching west towards Slovenj Gradec from Slovenska Bistrica. The 1st Battalion of the 112th Infantry Regiment had already deployed near Dravograd, supporting the 6th Border Regiment
• the 128th Infantry Regiment, which had been allocated to the 38th ID from the VKJ reserve at mobilisation, was concentrating near Ptuj
• the 38th Artillery Regiment (less its 2nd Battalion) was near Ptuj, while its 2nd Battalion was marching west from Maribor to its planned position at Slovenj Gradec
• the divisional machine-gun battalion, which had only 50 percent of its establishment of men and animals, was marching south from Maribor to Ptuj
• the remainder of the divisional units were mobilising in Slovenska Bistrica, Maribor, Ptuj and Ljubljana

5–6 April

The border between Germany and Yugoslavia was largely unsuitable for motorised operations due to the mountainous terrain.^[30] Due to the short notice of the invasion, the elements of Generaloberst^{[lower-alpha 4]} Maximilian von Weichs's invading German 2nd Army that would make up LI Infantry Corps and XXXXIX Mountain Corps had to be transported from Germany, German-occupied France and the Nazi puppet Slovak Republic, and nearly all encountered difficulties in reaching their assembly areas on schedule.^[32] In the interim, the Germans formed a special force under the code name Feuerzauber (Magic Fire). This force was initially intended to merely reinforce the 538th Frontier Guard Division, which was guarding the German border. On the evening of 5 April, a particularly aggressive Feuerzauber detachment commander, Hauptmann Palten, led his Kampfgruppe Palten across the Mura river from Spielfeld and, having secured the bridge, began attacking bunkers and other Yugoslav positions on the high ground, and sent patrols deep into the Yugoslav border fortification system. Due to a lack of Yugoslav counter-attacks, many of these positions remained in German hands into 6 April.^[30]

On the morning of 6 April, German aircraft conducted surprise attacks on Yugoslav airfields in the 7th Army area, including Ljubljana.^[33] For example, at 07:00, Messerschmitt Bf 109E fighters of Jagdgeschwader 27 strafed Ljubljana airfield, attacking hangars and some Potez 25 biplanes.^[34] The LI Infantry Corps, commanded by General der Infanterie^{[lower-alpha 5]} Hans-Wolfgang Reinhard, was tasked with attacking towards Maribor then driving towards Zagreb. The XXXXIX Mountain Corps, under General der Infanterie Ludwig Kübler, was to capture Dravograd then force a crossing on the Sava river at Zidani Most.^[35] At 05:00 on 6 April,^[36] LI Infantry Corps captured the Mura bridges at Mureck and Radkersburg (opposite Gornja Radgona) undamaged.^[37] One column of LI Infantry Corps pushed towards Maribor from Mureck, and the other pushed on from Gornja Radgona through Lenart towards Ptuj. Some time later, other elements of LI Infantry Corps attacked the area between Sveti Duh and Dravograd. The 7th and 8th Border Regiments met these attacks with fierce resistance, but were forced to withdraw due to German pressure.^[36]

Generalmajor^{[lower-alpha 6]} Benignus Dippold's 183rd Infantry Division of LI Infantry Corps captured 300 prisoners, and a bicycle-mounted detachment of the division reached Murska Sobota in the sector of the right flanking Detachment Ormozki without meeting any resistance. Generalmajor Rudolf Sintzenich's 132nd Infantry Division, also from LI Infantry Corps, pushed south along the Sejanski valley towards Savci.^[37] By the end of the first day, LI Infantry Corps had occupied Gornja Radgona, Murska Sobota and Radenci, and had crossed the Drava near Sveti Duh. XXXXIX Mountain Corps captured border crossings on the approaches to Dravograd, but was held up by the 6th Border Regiment in mountain passes located further west at Ljubelj, Jezerski Vrh and Korensko sedlo.^[36] Late that day, German mountain pioneers destroyed some isolated Yugoslav bunkers in the area penetrated by Kampfgruppe Palten.^[30]

Dravograd

Maribor

German gains on 6 April (shown in red) and major German objectives (shown in blue). Dravograd is to the west, and Maribor to the east.

German Junkers Ju 87 Stuka dive bombers of Sturzkampfgeschwader 77, escorted by Messerschmitt Bf 109E fighters, attacked airfields in the rear area of the 7th Army later that day.^[34] This was followed by attacks by the Italian Air Force on Yugoslav troop concentrations in the 7th Army area.^[38] The Yugoslav Air Force was unable to interdict the Axis air attacks because the Hawker Hurricanes and Ikarus IK-2 aircraft of its 4th Fighter Regiment were based 240 kilometres (150 mi) away at Bosanski Aleksandrovac. After having been grounded for most of the day by poor weather, in the afternoon Bristol Blenheim Mk I light bombers of the Yugoslav 68th Bomber Group flew missions against airfields and railway stations across the German frontier at Graz, Fürstenfeld, Steyr and Wiener Neustadt in an attempt to interdict the assembling Germans.^[39]

By the close of the first day, the 7th Army was still largely mobilising and concentrating, and this, combined with delays caused by fifth column actions meant that nearly all the fighting was conducted by border troops. Fifth columnists delayed but did not engage in combat with Yugoslav troops. The 38th ID was deployed along the southern bank of the Drava, with the 128th Infantry Regiment and an artillery battalion in depth around Ptuj, the 45th Infantry Regiment and an artillery battalion on the right around Maribor and the 112th Infantry Regiment and an artillery battalion on the left were at Slovenj Gradec and marching north towards Dravograd. German and Italian air attacks interfered with the deployment of troops and command was hampered by reliance on civilian telegraph and telephone services.^[40]

On that day, Marko Natlačen—the governor of the Drava Banovina (province)—met with representatives of the major Slovene political parties, and created the National Council of Slovenia (Slovene: Narodni svet za Slovenijo, NszS), whose aim was to establish a Slovenia independent of Yugoslavia. When he heard the news of fifth-column-led revolts within the flanking 4th Army, the commander of the 7th Army, Divizijski đeneral Dušan Trifunović was alarmed, and proposed withdrawal from the border areas, but this was rejected by the commander of the 1st Army Group, Armijski đeneral Milorad Petrović.^[41]

7 April

In the early hours of 7 April, three Blenheims of the Yugoslav 8th Bomber Regiment took off from Rovine to bomb the railway junction at Feldbach, but became disoriented in bad weather. Only one aircraft found a target, bombing a bridge and road near Steyr before continuing on to Wiener Neustadt where it was hit by anti-aircraft fire and made an emergency landing.^[42]

Over the period 7–9 April, LI Infantry Corps held the lead elements of the 183rd and 132nd Infantry Divisions back to some extent while the rest of each division de-trained in Graz and made their way to the border.^[37] German forces along the front of the 7th Army continued to push towards Maribor and Dravograd on 7 April, against significant resistance from the 6th, 7th and 8th Border Regiments. The German thrusts towards Maribor broke through the Yugoslav defensive line Pesnica–Lenart–Sveta Trojica v Slovenskih Goricah–Kapelski Vrh, but those advancing towards Dravograd were held up by the 6th Border Regiment and a battalion of the 38th ID.^[43]

On the afternoon of 7 April, Trifunović again pressed Petrović to order a withdrawal from the border. Petrović accepted that this might become necessary if the situation on the immediate right flank of the 7th Army deteriorated further, but the idea was opposed by the chief of staff of the headquarters of the 1st Army Group, Armijski đeneral Leon Rupnik, who wryly suggested that Trifunović should personally lead night attacks to push the Germans back. At 19:30, the Yugoslav Supreme Command advised Petrović that he had approval to withdraw endangered units on the right wing of the 7th Army. Morale in the 7th Army started to decline due to fifth column elements encouraging soldiers to stop resisting the enemy.^[44]

8 April

On the night of 7/8 April, Petrović ordered Trifunović to begin to withdraw, first to a line through the Dravinja river, Zidani Most bridge and the right bank of the Krka river. Later in the day this was moved back to the line of the Kupa river.^[41] This ended the successful defence of the 38th ID and border guard units along the line of the Drava, and meant their withdrawal from Maribor.^[45] Disregarding orders from above, Palten exploited their withdrawal by leading his kampfgruppe south towards the town, and crossing the Pesnica river in inflatable boats, leaving his unit vehicles behind. In the evening, Palten and his force entered Maribor unopposed, taking 100 prisoners. For disregarding orders, Palten and his kampfgruppe were ordered to return to Spielfeld, and spent the rest of the invasion guarding the border. In the meantime, the forward elements of the two divisions consolidated their bridgeheads, with the 132nd Infantry Division securing Maribor, and the 183rd Infantry Division pushing past Murska Sobota,^[37] reaching Kapelski Vrh.^[46]

Some bridges over the Drava were blown before all elements of the 7th and 8th Border Regiments had withdrawn, but some soldiers were able to swim across, the rest being captured by the advancing Germans.^[45] German patrols reached the Drava at Ptuj, and further east at Ormož they found the bridge had been blown. Elements of the XXXXIX Mountain Corps had pushed forward to Poljana and Dravograd.^[46] The German troops received close air support from dive bombers and fighters during their advance, while medium bombers hit targets throughout the 7th Army area. The 4th Fighter Regiment clashed several times with German aircraft on 8 April without result. Three Blenheims of the Yugoslav 8th Bomber Regiment again flew a mission to attack a target in southern Austria, escorted by 4th Fighter Regiment Hurricanes, but the rest of the 8th Bomber Regiment was awaiting orders to bomb a rebelling Yugoslav regiment of the neighbouring 4th Army in Bjelovar – these orders were subsequently cancelled.^[47] The German orders for the following day were for LI Infantry Corps to force a crossing of the Drava near Varaždin on the right flank of the 38th ID and advance on Zagreb, while XXXXIX Mountain Corps were to drive towards Celje.^[46]

9 April

On 9 April, the Germans continued their advance,^[48] and all elements of both divisions of LI Infantry Corps had finally unloaded in Graz.^[49] In the meantime, the 7th Army continued rapidly withdrawing its right wing, while withdrawing its centre more slowly. The 38th ID continued to withdraw south from Ptuj through Krapina towards Zagreb, while the Mountain Detachment Triglavski on its left flank fell back to the southern bank of the Krka river. Units of LI Infantry Corps crossed the Drava along the line Maribor–Ptuj and further east, and continued to expand their bridgehead south of Maribor. Elements of XXXXIX Mountain Corps expanded their bridgehead at Dravograd.^[48] German aircraft again attacked airfields in the rear area of the 7th Army.^[50]

As the activities of Natlačen and his NszS were continuing, the Yugoslav Supreme Command ordered their arrest. Rupnik and the head of the operations staff of the headquarters of the 1st Army Group, Pukovnik^{[lower-alpha 7]} Franjo Nikolić, who were both Slovenes, hid the orders from Petrović and did not carry them out.^[41][51]

10 April

On the evening of 9 April, Weichs ordered the XXXXVI Motorised Corps of General der Panzertruppe^{[lower-alpha 8]} Heinrich von Vietinghoff to break out of its bridgeheads in the 4th Army's sector the following day. The thrust from the Zákány bridgehead was to drive straight west to Zagreb then continue west to cut off the withdrawing 7th Army.^[52] This attack was led by Generalmajor Friedrich Kühn's 14th Panzer Division, supported by dive bombers, and was a resounding success. By 19:30 on 10 April, lead elements of the 14th Panzer Division had reached the outskirts of Zagreb, having covered nearly 160 kilometres (99 miles) in a single day.^[53] Before it arrived, the Ustaše, supported by German agents, had proclaimed the creation of the puppet Independent State of Croatia (Croatian: Nezavisna Država Hrvatska, NDH).^[54] When it entered Zagreb, the 14th Panzer Division was met by cheering crowds, and had captured 15,000 Yugoslav troops, including 22 generals.^[55]

In the 7th Army sector, about 09:45, the LI Infantry Corps began crossing the Drava, but construction of a bridge near Maribor was suspended because the river was in flood. Despite this, the 183rd Infantry Division managed to secure an alternative crossing point, and established a bridgehead.^[52] This crossing point was a partially destroyed bridge, guarded by a single platoon of the 1st Bicycle Battalion of Detachment Ormozki, the formation on the immediate right flank of the 38th ID. This crossing, combined with the withdrawal of the 38th ID from the line from Slovenska Bistrica–Ptuj, exposed the left flank of Detachment Ormozki. It attempted to withdraw south, but began to disintegrate during the night of 10/11 April.^[56]

That same night, the 1st Mountain Division, the most capable formation of XXXXIX Mountain Corps, had de-trained, crossed the border near Bleiburg, and advanced southeast towards Celje, reaching a point about 19 km (12 mi) from the town by evening.^[53] The rest of the XXXXIX Mountain Corps encountered little resistance, and by nightfall had reached the line Šoštanj–Mislinja.^[57] Luftwaffe reconnaissance sorties revealed that the main body of the 7th Army was withdrawing towards Zagreb, leaving behind light forces to maintain contact with the German bridgeheads. When it received this information, 2nd Army headquarters ordered LI Infantry Corps to form motorised columns to pursue the 7th Army south, but extreme weather conditions and flooding of the Drava at Maribor on 10 April slowed the German pursuit.^[37]

On 10 April, as the situation was becoming increasingly desperate throughout the country, Simović, who was both the Prime Minister and Chief of the General Staff, broadcast the following message:^[58]

All troops must engage the enemy wherever encountered and with every means at their disposal. Don't wait for direct orders from above, but act on your own and be guided by your judgement, initiative, and conscience.

During the night of 10/11 April, XXXXIX Mountain Corps was ordered to bridge the Savinja river at Celje, then advance towards Brežice on the Sava, and LI Infantry Corps was directed to link up with the 14th Panzer Division which would then drive west to Karlovac.^[59]

11 April

On 11 April, Ustaše elements captured the staff of the 7th Army at Topusko and handed them over to the Germans shortly thereafter,^[60] and the 7th Army effectively ceased to exist as a formation.^[61] Chaos ensued throughout the 7th Army, whose Croat and Slovene soldiers could hear fifth column radio broadcasts telling them of their pending encirclement by the Germans and encouraging them to return to their homes and not fight against the invaders. This was reinforced by Natlačen and his NszS, who had distributed leaflets on the night of 10/11 April urging soldiers not to resist the Axis troops. To maintain public order, the NszS also formed a "Slovenian Legion" on 11 April, and encouraged Slovene nationalists among the 7th Army to join it. This force, split into a dozen units and totalling 2,000–3,000 men, then began to assist the Germans in disarming units of the 7th Army, but did not engage in combat with Yugoslav troops. The NszS authorised Natlačen to negotiate with the Germans for the creation of a Slovene client state along the lines of the NDH and the Slovak Republic, and Natlačen appointed the Ljubljana police chief Lovro Hacin to make contact with the Germans.^[62]

Proxies for the NszS approached Generalmajor Hubert Lanz, the commander of the 1st Mountain Division, when his formation closed on Celje, but Lanz was not empowered to negotiate with civilians, and sought direction from higher headquarters. All German commanders were authorised to negotiate with the commanders of Yugoslav military formations so long as they agreed to surrender all weapons. Later that day, Lanz was authorised to meet with Natlačen the following day, and XXXXIX Mountain Corps took Celje.^[63] Held up by freezing weather and snow storms, LI Infantry Corps was approaching Zagreb from the north,^[55] and broke through a hastily established defensive line south of Ptuj between Pregrada and Krapina.^[63] Bicycle-mounted troops of the 183rd Infantry Division turned east to secure Ustaše-controlled Varaždin in the 4th Army sector. In the evening, LI Infantry Corps entered Zagreb and relieved the 14th Panzer Division but lead elements of that division had already thrust west from Zagreb into the rear of the withdrawing 7th Army and captured Karlovac.^[55][63]

Around 12:00,^[55] the Italians went over to the offensive against the formations of the 7th Army on the left flank of the 38th ID, with the 3rd Alpine Group tasked to advance to the line Selca–Radovljica, XI Corps to push via Logatec to Ljubljana, VI Corps to drive on Prezid, and V Corps to advance south from Fiume towards Kraljevica then Lokve.^[61][63] There was little significant resistance to the Italians, and by the end of the day they had captured Sušak, Bakar, Delnice, Jesenice, Vrhnika, Logatec and Ljubljana.^[63] To assist the Italian advance, the Luftwaffe attacked Yugoslav troops in the Ljubljana region. The Italians captured about 30,000 troops of the 7th Army waiting to surrender near Delnice.^[55] When the Italian 14th Infantry Division Isonzo entered Ljubljana, a delegate of the NszS greeted its commander, Generale di Divisione^{[lower-alpha 9]} Federico Romero, and symbolically handed him the keys to the city. An official reception was held for Romero that evening, attended by Natlačen and most of the members of the NszS, but because Natlačen and the council preferred that the Germans occupy Ljubljana, he asked Romero for permission to travel to Celje the following day to meet with Lanz.^[64]