Decisive battle between the Georgians and the Seljuk Turks of Rüm near Basian, in the vicinity of Erzurum (in modern Turkey); the date is usually given as 1203 but recent research suggest that the battle was fought in the summer of 1202. Under the rule of Kings David IV Aghmashenebeli and Giorgi III, Georgia emerged as one of the most powerful states in the Near East. The reign of Queen Tamar (1178–1213) further underscored Georgian might after a large Islamic coalition was crushed in the battle of Shamkhor in 1195. Alarmed by the Georgian success, Sultan Rukn ad-Din Suleiman Shah of Rüm (1196–1204) rallied the forces of the Muslim principalities against Georgia. The massive Islamic army (estimates range between 150,000–400,000 men) advanced toward the Georgian borders in 1203 and was met by the 90,000-strong Georgian army under David Soslani at Basian. The Georgian army was deployed with western (apkhazni da imerni) and eastern (amerni da her-kakhni) Georgian troops on flanks and some 40,000 men under Shalva and Ivane Akhaltsikheili in the center while Zakaria Mkhagrdzeli led the advance guard.
The Georgians initially made an unexpected attack with their advance guard on the Muslim army and spread confusion among the enemy troops. Sultan Rukn ad-Din Suleiman managed to rally his forces and counterattacked but was surprised by coordinated flanking attacks which routed his forces. Still, both sides suffered heavy casualties in the bitterly contested battle. The victory at Basian secured the Georgian preeminence in the region. Exploiting her success in this battle, Queen Tamar annexed Arran and Duin in 1203 and subdued the Emirate of Kars, Armen-Shahs and the emirs of Erzurum and Erzinjan. The Georgians then carried war into Azerbaijan and advanced as far as Ardabil and Tabriz in 1208 and into Qazvin and Khoy in 1210. These victories brought Georgia to the summit of its power and glory, establishing a pan-Caucasian Georgian empire that extended from the Black Sea to the Caspian and from the Caucasus Mountains to Lake Van.