At the end of 1915, the character and role on the prospects of future operations in the southern part of the Balkan peninsula were not yet clear for the two belligerent sides. After the land link with the Ottoman Empire, for the central powers and more precisely for Germany, the Balkans lost importance because it was concentrated on the Macedonian Front and mainly on the Western Front. Germany also encouraged Greece to join its side, taking into account its neutrality. Moreover, for Austria-Hungary and Bulgaria, the Balkans remained very important and its generals exalted the entire conquest of the peninsula and the withdrawal of the small expeditionary force from the Entente.
On the other hand, an important dichotomy existed among the main strengths of the Entente. Britain believed that without Greece on the side of the Entente, Serbia would be lost. While France believed that a significant military presence in the southern part of the Balkans was necessary, especially after the failure of the Dardanelles, for Romania and Greece not to join the central powers. At the same time, in Thessaloniki, the Allies began to build a military base and the British and French armies of General Maurice Sarrail were already present in the region. In December 1915, the French staff sent General Noël de Castelnau on a mission to the Balkans to examine the situation on the ground and the troops of the Allies, but also the possibility of developing the Macedonian Front. Six months later, General Sarrail was appointed commander-in-chief of the Allied army at the Macedonian Front, including the army stationed in Macedonia. This Allied army controlled about 30,000 square kilometres of territory. The population of this part of Macedonia was not hostile to the Allied army, but in view of the destruction caused by previous military conflicts, they distanced themselves from them. On the other hand, the Allies had doubts about the local population, very often considered to be dedicated to the Ottoman Empire and Bulgaria. Thessaloniki was at the centre of this area, a large cosmopolitan city with its history and a cross between cultures and ethnic groups (Jews, Turks, Greeks, Macedonians, Bulgarians, Vlachs, Roma and others), which had been included in the Greek state since 1912. After conducting analyses and drawing up additional plans, the Allied army deployed north of Thessaloniki, occupying a length of about 120 km. During the first half of 1916, the line of defence expanded increasingly, with various buildings and infrastructure managed by thousands of Allied soldiers and local civilians. Trenches, wells and canals were dug, wetlands drained, roads constructed and repaired. At the same time, thousands of French soldiers were transported by ships from Marseille and Toulon (South France) or even Otranto (Southern Italy) to the port of Thessaloniki. The Zeytinlik camp was the center of this military force, located 5 km northeast of Thessaloniki, near the Vardar River.