North of Lake Van, near the fortress of Malāzgird, the Saljūq sultan Alp Arslan — his army a fraction of the Roman host, his shroud worn over his armour by the famous account — broke the army of Romanos IV Diogenes on a Friday in Dhū al-Qaʿdah 463. The emperor himself was brought captive to the sultan's tent, treated with courtesy that the sources set against Constantinople's later cruelty to him, and released for ransom and treaty.
The defeat mattered less than the decade of Roman civil war it detonated: the Anatolian plateau lay open, Turkmen migration flowed in, and within twenty years there was a Sultanate of Rūm — the soil in which, four centuries later, the Ottoman conquest of 857 AH grew.
The Friday is certain; the Hijri day differs across conversions, so this entry stays at month precision.