Excerpts from Books and Wikipedia
"The Byzantine-Seljuq Wars were a series of decisive battles that shifted the balance of power in Asia Minor and Syria from the Byzantine Empire to the Seljuq Turks. Riding from the steppes of Central Asia, the Seljuq Turks replicated tactics practiced by the Huns hundreds of years earlier against a similar Roman opponent but now combining it with new-found Islamic zeal; in many ways, the Seljuq Turks resumed the conquests of the Muslims in the Byzantine–Arab Wars initiated by the Rashidun, Umayyad and Abbasid Caliphate in the Levant, North Africa and Asia Minor." [Wikipedia] "In about 1038, a group of nomadic Turkish tribes dominated by the Seljuks swept out of Central Asia. In 1055 they occupied Baghdad and went on to conquer Armenia. Alarmed by the approaching threat, the Byzantines marched east from Constantinople under Emperor Romanus Diogenes, but they suffered a crushing defeat at Manzikert in 1071. This drove the Byzantines out of Asia Minor and ultimately provoked the Crusades." [DK Timelines, p. 174]