The Salonika campaign began on the 5th of October 1915 when one British and two French divisions were landed at the Port of Salonika in neutral Greece the troops had been sent to deter Bulgaria from joining an Austro-German attack on Serbia and they’d been invited to land by the Greek Prime Minister Venizelos
By late October 1915 the British and French troops were in southern Serbia trying to maintain contact with the retreating Serbs who were under pressure from German Austrian Hungarian and Bulgarian armies the Serbs could no longer defend their country and decided to undertake an epic march across the mountains of Albania in terrible weather conditions here the survivors were rescued by British and French warships and taken to the island of Corfu.
Bulgarian army now turned its attention to the allied force in southern Serbia in heavy snow on the 7th of December 1915 elements of the second Bulgarian army smashed into the 10th Irish division its improvised line on Kosturino ridge. The Irish were pushed back and after a week all British and French troops were back on Greek soil and heading for Salonika
The allied war leaders decided to maintain a military force in the Balkans the reason for this was to establish and to secure Greek neutrality and to encourage the Romanians to join the war against the Central Powers
The British and French troops then spent five months building defences around the port of Salonika in case of a Bulgarian attack these defences stretched from the mouth of the river Vardar right round to the village of Stavros on the Aegean Sea. These defences received the nickname The Birdcage line
The Allied commander at Salonika decided that the Bulgarians were not going to attack the port so he decided to move his men northwards towards Doran the Allied forces quickly spread out and established a front line of around 250 miles in length stretching from the Adriatic coast of Albania round the mouth of the Struma River on the Aegean. To hold this line the allies deployed about 600,000 soldiers with contingents from Britain France Italy Russia and Serbia.