Following the alternate Gorlice Tarnow offensive in the summer of 1915, the Central Powers finally start planning for an offensive against Serbia in earnest. Angered by Austrian floundering the German OHL under Falkenhayn dispatches one of its most competent generals in Mackensen to take command. Due to the Habsburg Empire contributing more troops than it did historically - Italy is still neutral at this point - an agreement is struck that Mackensen de jure shares overall command with Archduke Eugen, who in practice just co-signs and rubber stamps Mackensen’s orders.

With the 5th Austro-Hungarian army approaching from Bosnia and Bulgaria joining on the side of the Central Powers, Serbia is defeated a bit more decisively than it was historically. Importantly the Serbian retreat is cut off by the Austrian 5th Army under Pflanzer-Baltin who manages to occupy the passes to Albania before the bulk of the Serbians can retreat that way. In the following large encirclement about 100.000 more Serbians are captured as POWs than historically.

While the Entente still lands two divisions in Salonika, as it did historically, there is no Serbian army to reconstitute to bring the fight back to the Bulgarians. Therefore no Salonika front ever seriously forms. To the contrary the Salonika incident leads to Venizelos being discredited in Greese and authority remaining with the King, who insists that only strict neutrality can save Greece. The ongoing occupation of several Greek islands and a small Entente presence in Salonika even against the will of the Greek government becomes a problem for the Entente propaganda. It is hard to maintain the line that it is fighting for the self determination fo the small countries when it is occupying parts of a small nation without consent.

Likewise Italy, still neutral at this point in time, lands some forces in Albania to protect its interests there. While not at war (yet), a tenous Albanian front forms where terrible logistocs mean that Austrians and Bulgarians on one side and Italians on the other mostly just stare at each other angrily while dying of Malaria and other diseases.