The Battle of Manzikert was fought between the Roman Empire and the Seljuq Turks on the 26th August, 1071, near the fortress of Manzikert in Cappadocia. It was important in bringing an end to the Turkic migrations that had threatened the empires of the Middle East for centuries, and in halting the slow decline of the Roman Empire.
By the 11th century the Roman Empire was corrupt, decaying and on the brink of collapse. It had recently bankrupted itself and decimated its armies trying to reconquer the Balkans from the Bulgars, and still it was under immense pressure from powerful neighbours. At the same time the ambitious aristocracy were competing for power, and shortly before Manzikert several claimants to the purple had fought a bloody civil war for the throne.
Meanwhile, the Seljuq clans had been expanding out from the original Turkic homeland in central Asia. In 1040 they defeated the Bagratids at the Battle of Dandanaqan, but suffered such heavy casualties in the process that they did not make any attempt at ruling the area. Instead the Seljuqs moved on, laden with plunder, in search of easier pickings - which Rome seemed to be ideally placed to provide.
The Seljuqs were utterly defeated and returned to Khorasan. Over the next few decades they declined in power and were eventually absorbed by other Turkic confederations such as the Khwarezmians.
Alp Arslan was captured and was taken as a prisoner to Antioch. There he was treated with all the respect due to a foreign king, and eventually he married a Roman princess and converted to Islam. In 1077 he was released from captivity and given an escort to take him back to his own people, but was assassinated en route on the orders of the new Seljuq khan, who was doing his best to eliminate all potential rivals. Alp Arslan's descendants by his second wife remained in Antioch and were eventually assimilated to Roman society, becoming the long-lasting aristocratic family of the Tzagrioglou.
Never again would the Turkic peoples venture so far west, ensuring that Anatolia remains Greek to this day. The battle prompted a revival of both the Roman Empire and the Bagratid realms, preparing them for the Mongol invasions of the region that would come two hundred years later.