Salonika, expedition to

In World War I, joint Anglo‐French expedition to help Greece against Bulgaria October 1915, which remained in the area, reinforced by Serbs, until the end of the war.

In September 1915, fearful of Bulgaria's intentions, Greece requested a reinforcement of 150,000 troops from the British and French governments. The Allies agreed and the first troops landed at Salonika 3 October 1915, including British troops from Gallipoli. By the end of October there were about 40,000 troops in Salonika, mostly French. On 11 October Bulgaria invaded Serbia and the Allies advanced to make contact with the southern Serbian army and halt the invasion. They failed due to the greater numbers of the Bulgarian forces and the Allies retreated back into Greece 12 December.

Despite having been of no assistance to the Serbians, it was decided to maintain a force in Salonika and the expedition was reinforced: by summer 1916 it consisted of 300,000 Allied troops and 100,000 Serbians plus elements of Russian and Italian troops. In July this force advanced up the Struma valley, the French linking up with the Serbians near Vardar. The Bulgarians attacked the centre of the Allied line but in spite of some local successes they were eventually driven back, with the Serbians and French pressing on their right and the British turning their left flank.

Monastir fell to the Allies November 1916, after which the lines stabilized and trench warfare ensued until the spring of 1918 when General Franchet d'Esperey took command of the Allied forces in the area. By this time the Greek Army had been reorganized and had 150,000 troops available, and after careful planning a fresh offensive was begun September 1918 which, within two weeks, obtained Bulgaria's unconditional surrender.

After this the Allied force cleared all German and Austrian troops from the Balkans, and on 9 November a strong Serbian force crossed the Danube and was headed for Bucharest when the war ended.