The Battle of Manzikert or Malazgirt was fought between the Byzantine Empire and the Seljuk Empire on 26 August 1071 near Manzikert, Iberia (modern Malazgirt in Muş Province, eastern Turkey). The decisive defeat of the Byzantine army and the capture of the emperor Romanos IV Diogenes played an important role in undermining Byzantine authority in Anatolia and Armenia, and allowed for the gradual Turkification of Anatolia. Many Turks, travelling westward during the 11th century, saw the victory at Manzikert as an entrance to Asia Minor.

The brunt of the battle was borne by the Byzantine army's professional soldiers from the eastern and western tagmata, as large numbers of mercenaries and Anatolian levies fled early and survived the battle. The fallout from Manzikert was disastrous for the Byzantines, resulting in civil conflicts and an economic crisis that severely weakened the Byzantine Empire's ability to defend its borders adequately. This led to the mass movement of Turks into central Anatolia – by 1080, an area of 78,000 square kilometres (30,000 sq mi) had been gained by the Seljuk Turks. It took three decades of internal strife before Alexius I (1081–1118) restored stability to Byzantium. Historian Thomas Asbridge says: "In 1071, the Seljuqs crushed an imperial army at the Battle of Manzikert (in eastern Asia Minor), and though historians no longer consider this to have been an utterly cataclysmic reversal for the Greeks, it still was a stinging setback." It was the only time a Byzantine emperor became the prisoner of a Muslim commander, and the first time since Valerian that a Roman emperor was captured alive by an enemy force.

Background

Although the Byzantine Empire had remained strong and powerful in the early Middle Ages, it began to decline under the reign of the militarily incompetent Constantine IX Monomachos and again under Constantine X Doukas – a brief two-year period of reform under Isaac I Komnenos merely delayed the decay of the Byzantine army.

About 1053, Constantine IX disbanded what the 11th century Byzantine historian John Skylitzes called the "Iberian Army", which consisted of 50,000 men. Skylitzes' contemporaries, the former officials Michael Attaleiates and Kekaumenos, agree that by demobilizing these soldiers, Constantine did catastrophic harm to the empire's eastern defenses. Constantine made a truce with the Seljuks that lasted until 1064, when a large Seljuk army under Alp Arslan attacked the theme of Iberia and took Ani; after a siege of 25 days, they captured the city.

In 1068, Romanos IV Diogenes took power and, after some military reforms, conducted two major campaigns to combat the Seljuks and their Mirdasid allies. He retook the city of Hierapolis in 1068 and chased after Turkoman armies that were raiding across Anatolia, with limited success, but he was unable to score a decisive victory in 1069. In 1070, Manuel Komnenos lead an expedition against the Seljuks, thwarting an attack against Iconium with a counterattack. However, he was then defeated in the Battle of Sebasteia by Arisighi, Alp Arslan's brother-in-law, who then joined Byzantines, providing them with information regarding Seljuk and tactics. Alp Arslan then sent Afshin Bey to get Arisighi back, but he was refused at Chrysopolis, causing him to sack and pillage multiple Byzantine cities in retaliation.