Following the invasion of Serbia by Austro German forces and the Bulgarian Army in October 1915, Anglo French forces were dispatched north from the Greek port of Salonika (Thessalonika) in Macedonia to assist the beleaguered Serbian Army. Too late to prevent the defeat (and subsequent retreat) of Serbian forces, the Allied troops under French Commander Sarrail withdrew to the Salonika town area and via an extensive system of trench lines established a strong defensive position in the face of Bulgarian and German forces threatening on the frontier. A front line defensive perimeter of near 110 kilometres was established and in response to Bulgarian aggression limited Allied attacks were made in the direction of Monastir across the Serbian border in 1916-1917. The campaign, which drew in some 600,000 French, British and Serbian troops by early 1917 was fought in areas plagued with malaria carrying mosquitoes and illness effected the great majority of the troops serving there. Although the Allies effected a significant breakthrough into Bulgaria in late 1918 the campaign has received much criticism as a wasteful distraction from the main theatre of war, the Western Front.