Battle of Aivatovo

From the outbreak of war on 5 October, the combined forces of the Balkan allies began a converging advance on Thessaloniki, the largest city in Ottoman-ruled Macedonia. The Greek army advanced from Thessaly through the valley of the Bistritsa River, while the Bulgarian 7th Rila Infantry Division moved down the Struma River. After the successful Battle of Kumanovo, in which they routed the main Turkish forces in Macedonia, the Serbs also joined the race for Thessaloniki. Despite the allies' lack of coordination, the relatively small Turkish forces were unable to resist them. Between 9 and 13 October, the Struma Corps suffered defeats at Bulgarian hands near Simitli and Krupnik. On 20 October, the Turkish VIII Corps was defeated by the Greeks at the Battle of Yenidje Vardar. Soon afterwards, the Struma Corps abandoned the Rupel Gorge and withdrew towards Thessaloniki, pursued by the Rila Division. By this time the Ottoman troops were demoralised, and many soldiers deserted or surrendered to the allies. On 22–23 October, the Bulgarians passed through the gorge and occupied Demir Hisar with minimal resistance from the Turkish rearguard. The advance guard of the 7th Rila Division entered Kukush on 25 October together with Serbian cavalry from the Danube Cavalry Regiment.

The battle ended in victory for Bulgaria. The Bulgarian troops opened a route to Thessaloniki. On 27 October, some Bulgarian troops, including a cavalry unit commanded by Major G. Anastasov and Georgi Monchev's band, entered through the city's northern districts. They were enthusiastically welcomed by the Bulgarian and Jewish population, who decorated their homes with Bulgarian flags. Despite this triumphant moment, the advance of the main Bulgarian forces into the city was halted at the Greeks' emphatic request of 27 October. They arranged separate negotiations with the city's commander, Hasan Tahsin Pasha, who surrendered himself and his troops to the Greek army. Thus, Thessaloniki's surrender was negotiated between the Greeks and Turks before the main Bulgarian forces entered the city.