Belgrade fell to the armies of the Central Powers on October 9th 1915 as the Allies launched a belated attempt to support Serbia by landing troops in neighbouring Greece.
Bulgaria joined Germany and Austria-Hungary in the autumn invasion of Serbia, attacking the country in the south.
In overall command was August von Mackensen, the German general who’d led the Gorlice-Tarnów breakthrough against the Russians in Poland in May.
Encouraged by the Central Powers, Bulagaria’s aim was to recover territory lost in the Second Balkan War of 1913.
Britain and France were still engaged in the faltering Gallipoli campaign. But troops were sent to the Greek port of Salonika (present-day Thessaloniki) with the intention of helping the Serbs.
Tensions over the war in neutral Greece provoked a political crisis, with a split between supporters of the pro-Allied Prime Minister Elefthérios Venezélos and King Constantine I, brother-in-law of Kaiser Wilhem II.
Serbian forces, overwhelmed by the combined attack of the Central Powers and their new ally Bulgaria, began a full retreat in late autumn, their numbers swollen by fleeing civilians.
Thousands died crossing the mountains of Montenegro in the first snows of winter. Those who reached the Albanian coast were evacuated to Corfu, and later Salonika.
The Anglo-French advance from the Greek port was too little and too late to save Serbia. It remained under occupation until the closing weeks of the First World War.
Victory allowed the Central Powers to open the railway line from Berlin to the Ottoman capital, Constantinople (now Istanbul) and supply Turkey.
By December 1915, the Allied forces were back where they’d started. But the Salonika garrison remained, eventually numbering hundreds of thousands of troops from Britain and France, their colonies, Russia, Italy, Greece and Serbia.
A major offensive in September 1918 ended with the defeat of Bulgaria.
Read more about Allied operations at Salonika from 1915-18 on the Salonika Campaign Society website.
Sources: Wikipedia/various
Images courtesy of Imperial War Museums © IWM Q 52354
Posted by: Peter Alhadeff, Centenary News