[3] Balkan Army was formed on 25 July 1914 after the chief of the general staff, Franz Conrad von Hötzendorf, issued the mobilisation order joining Minimalgruppe Balkan (Balkan Minimal Group), a force consisting of the Fifth and Sixth armies dedicated for operations against Serbia and Montenegro,[4] with B-Staffel (B-Contingent), the reserve force, renamed Second Army ready to be deployed against Serbia to assist Minimal Group but also to be deployed against the Russians in Galicia if needed.

[7] On 7 August 1914 Balkanstreitkräfte was placed under the command of Bosnia-Herzegovina’s military governor Oskar Potiorek,[b] by the chief of the Austro-Hungarian General Staff, Franz Conrad von Hötzendorf.

Before the end of the Summer all Balkanstreitkräfte's units had retreated out of Serbia, the first Allied victory of the First World War[12] On 8 September Potiorek launched a second invasion threatening Belgrade, however at the Battle of the Drina the 5th Army was pushed back into Bosnia while the 6th was also force to retreat on 25 September to avoid encirclement from Serbian and Montenegrin forces.

[13] Starting on 24 October, the Valjevo offensive enjoyed some success allowing the Balkan Army to reach deep into northern Serbia.

In the face of total annihilation the Balkanstreitkräfte was forced to evacuate Serbia yet again abandoning Belgrade which was recaptured by the Serbs on 15 December.