The Battle of Yenidje, also transliterated as Yenice (, Battle of Giannitsa), 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. 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. Background During 1912, Greece, Serbia, Bulgaria, and Montenegro joined in a Balkan League against the Ottoman Empire. Fearing a new war in the Balkans, the Ottomans mobilized their armed forces on 14 September and began transferring units to Thrace; the Balkan League responded in kind. On 30 September, the League presented the Ottomans with a list of demands regarding the rights of its Christian population. The Ottoman Empire rebuffed the demands, recalled its ambassadors in Sofia, Belgrade and Athens and expelled the League's negotiators on 4 October. The League declared war against the Ottomans, while Montenegro had already began military operations on 25 September. The Greek Army of Thessaly crossed into Ottoman territory in the early morning hours of 5 October, finding most border posts to be abandoned. The first major clashes took place the following day when the 1st and 2nd Greek Divisions attacked Elassona, resulting in an Ottoman withdrawal towards Sarandaporo. At 7 a.m. on 9 October, the Greek infantry began its assault on Sarandaporo. The 1st, 2nd and 3rd Divisions attacked the Ottoman main line frontally. In the meantime, the cavalry brigade and the 4th and 5th Divisions conducted a flanking maneuver from the west with the intention of striking the rear of the Ottoman positions. The Konstantinopoulos Evzone detachment struck from the east of the pass. Fearing that they would be encircled by the Konstantinopoulos Evzone detachment, the Ottomans