Serbian campaign

Battle context

The Serbian campaign encompassed two distinct phases that shaped the Balkan theater of the First World War. Austria-Hungary's 1914 invasion failed, leaving Serbia in Allied hands, but a renewed Central Powers offensive in 1915 — drawing on Austrian, German, and Bulgarian forces under commanders including August von Mackensen — succeeded in occupying the country and forcing Serbian forces into a grueling retreat. The occupation removed Serbia as an active front until 1918, when Allied forces broke through in Macedonia and Serbian and Allied troops liberated the territory. The campaign's scale was severe: Allied casualties reached 450,000 against a Central Powers force roughly half the size, reflecting the attrition exacted on the defending side across both phases. Serbia's eventual liberation in 1918 contributed to the collapse of the Central Powers position in the Balkans in the war's final weeks.