Despite being perceived as impregnable by its defenders, the main body of the Greek forces managed to advance deep inside the pass, while auxiliary units broke through the Ottoman flanks.

[2] Venizelos followed in Theotokis' footsteps by rearming and retraining the military, enacting extensive fortification and infrastructure works, purchasing new weapons, and recalling the reservists for training.

[3] The British mission was headed by Rear Admiral Lionel Grant Tufnell, who placed an emphasis on gunnery practice and fleet maneuvers, while his assistants introduced a new fuse for the Whitehead torpedo.

[4] The French mission under Brigadier General Joseph Paul Eydoux focused its attention on improving discipline and training senior officers in large formation operations.

The treaty was signed on 15 July 1912, with the two countries agreeing to assist each other in case of a defensive war and to safeguard the rights of Christian populations in Ottoman-held Macedonia, thus joining the loose Balkan League alliance with Serbia, Montenegro and Bulgaria.

[11] The battle for Elassona lasted for three hours, with the Ottomans retreating to avoid encirclement, thus giving the troops manning the main defensive line at Sarantaporo additional time to reinforce their positions.

[14] The Ottomans had organized their defenses under the guidance of German military advisors, placing their artillery batteries and infantry in sheltered, camouflaged trenches on the ravine's steep slopes, allowing them to accurately fire along its entire length.

[16] The 5th Division advanced further to the west towards the village of Zampourda which was situated on the other bank of the Haliacmon River, with the intention of protecting the left flank of the Greek forces emerging from the Sarantaporo pass.

[17] Attacking from the east of the pass the Konstantinopoulos Evzone detachment overcame stiff resistance at Vlacholeivado and captured the village, but failed to advance further due to heavy fog.

Upon reaching the Porta Pass it engaged in a bloody clash with the defenders, securing its objective at 5 p.m.[19] The 5th Division and the Gennadis Evzone detachment were confronted by four Ottoman reserve battalions at Lazarades which held their ground until sunset.

Upon reaching their second defensive line, the Ottomans became aware of the 4th Divisions' seizure of Porta Pass and panic spread in their ranks and many soldiers fled, abandoning their equipment.

[20] On the morning of 10 October, the 4th Division charged down the northern slope of the Rahovo Mountain, surprising the Ottoman infantry and artillerymen who abandoned over twenty Krupp guns and engaged in a disorganized retreat.

[21][24] Following the declaration of war local authorities had detained all the Christian dignitaries from Servia and the surrounding villages with the intention of massacring them, a plan that was thwarted by Ottoman officer Omer Bey.