By 1917 a multinational Allied force under French General Maurice Sarrail numbering 500,000 troops faced the Bulgarian Army and German, Austro-Hungarian and Turkish units, totalling 300,000 men. The front line stretched from Albania to the mouth of the River Struma in Greece.
By March 1917 the British Salonika Force (BSF) under General George Milne held 90 miles (144 km) of front, including the key strategic position at Doiran.
Sarrail launched an offensive in April 1917, with French, Italian, Russian and Serbian troops. In support, the BSF attempted to capture Bulgarian positions around Doiran. When this offensive failed, static trench warfare continued until autumn 1918.
Living conditions for soldiers on both sides were harsh. Winter and summer brought extremes of climate and disease - especially malaria - caused many more casualties than fighting.
On 15 September 1918, Allied forces, directed by French General Louis Franchet d’Esperey, went onto the offensive. The BSF attacked at Doiran, helping French and Serbian troops to break the Bulgarian defences. Unable to stop this advance, the Bulgarian Army was forced into full retreat.
On 29 September, Bulgaria signed an armistice and fighting ceased the following day.