It formed part of the 2nd Army Group, and was responsible for the defence of the Yugoslav–Hungarian border along the Drava river from Slatina to the Danube.

The Kingdom of Serbs, Croats and Slovenes was created with the merger of Serbia, Montenegro and the South Slav-inhabited areas of Austria-Hungary on 1 December 1918, in the immediate aftermath of World War I.

It was formed around the nucleus of the victorious Royal Serbian Army, as well as armed formations raised in regions formerly controlled by Austria-Hungary.

The army budget remained tight, and as tensions rose across Europe during the 1930s, it became difficult to secure weapons and munitions from other countries.

[5] Consequently, at the time World War II broke out in September 1939, the VKJ had several serious weaknesses, which included reliance on draught animals for transport, and the large size of its formations.

[9][10] The weaknesses of the VKJ in strategy, structure, equipment, mobility and supply were exacerbated by serious ethnic disunity within Yugoslavia, resulting from two decades of Serb hegemony and the attendant lack of political legitimacy achieved by the central government.

Fifth column activity was also a serious concern, not only from the Croatian nationalist Ustaše but also from the country's Slovene and ethnic German minorities.

[13][14] Slavonski Brod and Tuzla were key centres for the mobilisation and concentration of the 2nd Army due to their good rail infrastructure.

Of the army-level support units, the 76th Artillery Regiment was mobilising far to the south in Mostar, and was unable to move to its concentration area near Đakovo due to a lack of draught animals.

[28] By the end of 6 April, the 30th ID held positions in Baranya on the line Batina—Beli Manastir—Drava, with its strongest flank on the left, closest to the Drava.

[31] During the first few days after the commencement of the invasion, there were exchanges of fire with Hungarian border guards, but the 2nd Army faced no direct attacks.

The 30th Divisional Cavalry Battalion was located in Kneževi Vinogradi, 11 kilometres (6.8 mi) southeast of Beli Manastir.

[33] The following day, the situation deteriorated significantly when General der Panzertruppe Georg-Hans Reinhardt's XXXXI Motorised Corps of the German 12th Army crossed the Yugoslav–Romanian border into the Yugoslav Banat and struck the 6th Army, halting its withdrawal and disrupting its ability to organise a coherent defence behind the Danube.

Generalmajor Walter Neumann-Silkow's 8th Panzer Division turned southeast between the Drava and Sava rivers, and meeting almost no resistance and with strong air support, had reached the left flank of the 2nd Army at Slatina by evening, despite poor roads and bad weather.

[35] Later that day, as the situation was becoming increasingly desperate throughout the country, Simović, who was both the Prime Minister and Yugoslav Chief of the General Staff, broadcast the following message:[35] 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.The 2nd Army was able to evacuate Baranja and organised a defence of the left flank of the 2nd Army Group, now threatened by the 8th Panzer Division, but Croat reservists began to desert their units due to the fifth column activities of the fascist Ustaše and their sympathisers.

[41] The XXXXVI Motorised Corps continued to push east south of the Drava, with the 8th Panzer Division capturing Našice, Osijek on the Drava, and Vukovar on the Danube, followed by Generalmajor Sigfrid Henrici's 16th Motorised Infantry Division which advanced east of Našice, despite bridge demolitions and poor roads.

[35] The 8th Panzer Division then destroyed a bridge over the Danube at Bogojevo,[44] and advanced on Lazarevac about 32 kilometres (20 mi) south of Belgrade.

[44] West of Belgrade, remnants of the 2nd Army Group tried to establish a line along the Sava, but XXXXVI Motorised Corps had already captured the bridges.

The Ustaše had captured Slavonski Brod without German assistance, but 2nd Army units recaptured the town and destroyed the bridge over the Sava.

On 14 and 15 April, tens of thousands of Yugoslav soldiers were taken prisoner by the Germans during their drive on Sarajevo in the centre of the country, including 30,000 around Zvornik and 6,000 around Doboj.