After their defeat at Sarandaporo, the Ottomans augmented the remnants of Hasan Tahsin Pasha's force with fresh reinforcements. Two divisions from east Macedonia, one reserve division from Asia Minor and one reserve division from Thessaloniki; bringing the total Ottoman forces in the area to 25,000 men and 36 artillery pieces.^[10] The Ottomans chose to organize their main defensive line at Yenidje either because of the town's religious importance for Macedonia's Muslim population or because they did not wish to fight too close to Thessaloniki.^[12] The Ottomans dug their trenches at a 130-meter (400 ft) high hill which overlooked the plain west of the town. The hill was surrounded by two rough streams, its southern approaches were covered by the swampy Giannitsa Lake while the slopes of Mount Paiko complicated any potential enveloping maneuver from the north.^[12] On the eastern approaches to Yenidje, the Ottomans reinforced the garrisons guarding the bridges across the Loudias River, the rail line at Platy and Gida.^[13]

On 18 October, the Greek general command ordered its troops forward despite receiving conflicting intelligence reports regarding the disposition of the enemy troops.^[11] The 2nd and 3rd Greek Divisions marched along the same route towards Tsaousli and Tsekre respectively, both located north-east of Yenidje. The 1st Greek Division acted as the army's rearguard. The 4th Division headed towards Yenidje from the north-west, while the 6th Division circumvented the city further to west, intending to capture Nedir. The 7th Division and the cavalry brigade covered the right flank of the army by advancing towards Gida; while the Konstantinopoulos Evzone detachment was ordered to seize Trikala.^[14]

The Battle of Yenidje began when the Greek army attacked the Ottoman fortified position at Yenidje (now Giannitsa, Greece), which was the last line of defense for the city of Thessaloniki.

The rough and swampy terrain surrounding Yenidje significantly complicated the advance of the Greek army, most notably its artillery. In the early morning of 20 October, an infantry charge by the Greek 9th Evzone Battalion caused the Greek army to gain momentum, leading to the collapse of the entire western wing of the Ottomans. Ottoman morale plunged and the bulk of the defenders began fleeing two hours later. The Greek victory at Yenidje opened the way for the capture of Thessaloniki and the surrender of its garrison, helping shape the modern map of Greece.