during which he captured the regions between Tbilisi and the Çoruh river, Akhalkalaki and Alaverdi. Bagrat IV submitted to paying jizya to the Seljuks but the Georgians broke the agreement in 1065. Alp Arslan invaded Georgia again in 1068. He captured Tbilisi after a short battle and obtained the submission of Bagrat IV; however, the Georgians freed themselves from Seljuk rule around 1073–1074. In consolidating his empire and subduing contending factions, Arslan was ably assisted by Nizam al-Mulk, and the two are credited with helping to stabilize the empire after the death of Tughril. With peace and security established in his dominions, Arslan convoked an assembly of the states and in 1066, he declared his son Malik Shah I his heir and successor. With the hope of capturing Caesarea Mazaca, the capital of Cappadocia, he placed himself at the head of the Turkoman cavalry, crossed the Euphrates, and entered and invaded the city. Along with Nizam al-Mulk, he then marched into Armenia and Georgia, which he conquered in 1064. After a siege of 25 days, the Seljuks captured Ani, the capital city of Armenia. Byzantine struggle En route to fight the Fatimids in Syria in 1068, Alp Arslan invaded the Byzantine Empire. The Emperor Romanos IV Diogenes, assuming command in person, met the invaders in Cilicia. In three arduous campaigns, the Turks were defeated in detail and driven across the Euphrates in 1070. The first two campaigns were conducted by the emperor himself, while the third was directed by Manuel Comnenos, great-uncle of Emperor Manuel Comnenos. During this time, Arslan gained the allegiance of Rashid al-Dawla Mahmud, the Mirdasid emir of Aleppo. In 1071, Romanos again took the field and advanced into Armenia with possibly 30,000 men, including a contingent of Cuman Turks as well as contingents of Franks and Normans, under Ursel de Baieul. Alp Arslan, who had moved his troops south to fight the Fatimids, quickly reversed to meet the Byzantines. At Manzikert, on the Murat River, north of Lake Van, the two forces waged the Battle of Manzikert. The Cuman mercenaries among the Byzantine forces immediately defected to the Turkic side. Seeing this, "the Western mercenaries rode off and took no part in the battle." To be exact, Romanos was betrayed by general Andronikos Doukas, son of the Caesar (Romanos's stepson), who pronounced him dead and rode off with a large part of the Byzantine forces at