The Battle of Yenidje was a major battle between Greek forces under Crown Prince Constantine and Ottoman forces under General Hasan Tahsin Pasha and took place between October 19–20 (O.S.), 1912 during the First Balkan War. The battle 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, which had a Greek majority population.
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.
