Asia Minor–modern Turkey–was formerly inhabited by a variety of non-Turkic peoples. Most of these people spoke Indo-European languages and included the Hittites, Phrygians, and Luwians (Troy was probably a Luwian city). After the conquests of Alexander the Great, Asia Minor was mostly Hellenized and remained solidly Greek until the 11th century, with Armenians forming the majority in the eastern parts of the region, as they had since antiquity.
In the second half of the first millennium CE, Turkic peoples were gradually streaming into most of Central Asia from their original homeland in the Altai mountains of western Mongolia. They gradually displaced or assimilated both the settled and nomadic Iranian-speaking people. But how did they get all the way to Turkey, which has the largest concentration of Turkic peoples today?
In the 11th century, Turks began appearing at the edges of Asia Minor (Anatolia), which was then controlled by the Greeks. Many of the Turks were mercenaries in the employ of local Arab and Persian rulers to the east of the Byzantine Empire and Armenia, the dominant states in Asia Minor. In 1037, the Seljuk Empire, a Turkic state, was founded northeast of Iran in Central Asia and quickly overran much of Persia, Iraq, and the Levant. By the 1060s, the Seljuk Empire bordered Byzantine Asia Minor. It should be noted that the Turks were a minority, ruling a Persian, Arab, and Kurdish majority.
The main strategic threat to the Turks was the Fatimid Caliphate based in Egypt. The Fatimids were Ismaili Shia and ruled over Jerusalem and Mecca at that time while the Turks upheld Sunni Islam. The Sunni Caliph in Baghdad was their puppet. By this time, the Caliph had ceased to exercise any political role while the Seljuk sultans held the reigns of power. As was the case of many empires, many problems arose due to the conflicts between nomadic rulers and a sedentary population. Thus, many of the Turkic tribes under Seljuk rule actually posed a problem for the Seljuks since they were restless and sometimes raided settled populations ruled by the Seljuks. As a result, many of the Turkic tribes and families were placed on the frontiers of the Seljuk Empire, including on the frontier of the Byzantine Empire. Turkish raids into Asia Minor commenced, greatly annoying the Byzantines.
In 1045, the Byzantines conquered Armenia. Their frontier with the Seljuks was not particularly strong or pacified as a result of the intermittent warfare there. Additionally, many Armenians did not like the Byzantines and did not help them resist the Turkish raids. Eventually, by 1071, the Byzantines, exasperated at constant Turkish raiding, decided to move a large army to their borders to eliminate the Turkish threat once and for all. Unfortunately, this was not a particularly good idea, because their strength lay in manning border forts against lightly armed tribal warriors. By attempting to fight a pitched battle, they also risked total defeat.
Furthermore, the Seljuk Turks did not want to antagonize the Byzantines. Their state apparatus was directed against Egypt; it was only tribes that were barely under central Seljuk control that were raiding the Byzantines. Romanus IV Diogenes, the Byzantine Emperor, created a previously non-existent threat for the Seljuks by moving some 40,000 troops to his eastern border, thus alerting the Seljuk Sultan Alp Arslan to the threat from Asia Minor. Thus, the Byzantines, by diverting the Turks’ attention from Egypt, brought a Turkic army to Asia Minor from Persia and Central Asia.
The Seljuk and Byzantine armies met at Manzikert in eastern Turkey, where the Byzantines were crushed. This is arguably one of the most decisive battles in history, as it resulted in the eventual establishment of Turkish power in Asia Minor. It was likely that the battle was lost by the Byzantines due to treachery, because units commanded by generals belonging to alternative court factions in Constantinople simply never showed up for the battle, despite being in the vicinity, and returned home afterwards.
Sultan Alp Arslan captured Emperor Diogenes and and offered him generous terms before sending him home. However shortly afterwards, the Byzantine empire suffered a civil war between Diogenes and other contenders for the throne and several generals broke his treaty with the Turks. This left Asia Minor devoid of soldiers and gave the Turks good reason to occupy it. By 1081, they were across the Bosphorus Straits from Constantinople. Although the Byzantines and Crusaders later recovered some territory in Asia Minor, from then on, the majority of the region remained under Turkish control.
But groups of Turks ruled over many states in the Middle East and South Asia at this point in time. Why did they become the majority in Turkey? After the Seljuk victory, many Turks poured into Asia Minor, establishing little statelets, and ruling over the native population. Following the subsequent Mongol invasions, even more poured in, fleeing from their former lands in Persia and Central Asia. Unlike in many other cases, where a dominant minority eventually became assimilated into the majority population, because of the unstable, chaotic frontier situation, the Turks did not assimilate into the population. Indeed, many locals (ethnic Greeks and Armenians) attached themselves to Turkish warlords for protection as clients. This client-patron relationship spread out over many bands and tribes across Asia Minor and ensured that the majority of the population assimilated into the Turkish religion (Islam), language, and culture instead of vice versa.
This is a cultural process known as elite dominance, wherein a minority imposes its culture on the majority. The Turkification of Asia Minor is evident in the fact that genetically, the majority of today’s Turks are most closely related to Greeks and Armenians rather than Central Asian Turkic peoples, like the Uzbeks and Kazakhs. Thus, while the Turkic culture dominated in Asia Minor, the Turks themselves quickly merged genetically into the native population. Genetic studies show that around 15 percent of the Turkish genetic mixture derives from Central Asia.
Asia Minor was the most populous part of the Byzantine Empire, its heartland. Without it, the empire simply didn’t have enough resources to compete in the long run. Turkification was also helped by the fact that the Greeks were of a different religion than the Turks. Greeks converting to Islam would adopt Turkish language. Furthermore, in the later Ottoman Empire, the Turkish language prevailed at the official level, and not local languages. As a result of all these factors, densely populated Asia Minor became the region of the world with the largest concentration of Turkic-speaking peoples, far away from their original homeland in Central Asia.
ED: https://thediplomat.com/2016/06/the-epic-story-of-how-the-turks-migrated-from-central-asia-to-turkey/
The first people known to have occupied Central Asia were nomads who arrived from the northern grasslands of what is now Uzbekistan sometime in the first millennium B.C. They began to build an extensive irrigation system along the rivers of the region. In time cities such as Bukhara and Samarkand began to appear as centers of government and culture. By the fifth century B.C., the Bactrian, Soghdian, and Tokharian states dominated the region. As te silk route these settlements took advantage of this commerce by becoming centers of trade and in time became known as Mawarannahr (a name given the region after the Arab conquest) >
The wealth of Mawarannahr was a constant magnet for invasions and numerous intraregional wars were fought in Mawarannahr. Alexander the Great conquered the region in 328 B.C., bringing it briefly under the control of his Macedonian Empire. In the same centuries, however, the region also was an important center of intellectual life and religion. Until the first centuries after Christ, the dominant religion in the region was Zoroastrianism, but Buddhism, Manichaeism, and even Christianity also attracted followers. The conquest of Central Asia by Islamic Arabs, which was completed in the eighth century A.D., brought to the region a new religion and culture that continue to be dominant. The Arabs first invaded Mawarannahr in the middle of the seventh century through sporadic raids during their conquest of Persia.
The Arabs were led by a brilliant general, Qutaybah ibn Muslim, and were highly motivated by the desire to spread their new faith (the official beginning of which was in A.D. 622). The new religion brought by the Arabs spread gradually with the destiny of Central Asia as an Islamic region not being firmly established until the Arab victory over the Chinese armies in 750 in a battle at the Talas River.>
Under Arab rule, Central Asia retained much of its character, remaining an important center of culture and trade for centuries after the Arab conquest. However, until the tenth century the language of government, literature, and commerce was Arabic. Mawarannahr continued to be an important political player in regional affairs, supporting the Abbasid Caliphate in its struggle against the then-ruling Umayyad Caliphate.>
During the height of the Abbasid Caliphate in the eighth and the ninth centuries, Central Asia and Mawarannahr experienced a truly golden age. Bukhoro became one of the leading centers of learning, culture, and art in the Muslim world, its magnificence rivaling contemporaneous cultural centers such as Baghdad, Cairo, and Cordoba. Many of the greatest historians, scientists, and geographers in the history of Islamic culture were natives of the region. As the Abbasid Caliphate began to weaken and local Islamic states emerged as the rulers of Central Asia. the Persian language began to come intp the region as the language of literature and government. Under the Samanids and the Buyids, the rich culture of Mawarannahr continued to flourish.>
From the fifth to the ninth century AD Turkic tribes who lived in the great grasslands stretching from Mongolia to the Caspian Sea started to move permanently into the region. In the late tenth century, as the Samanids began to lose control of Mawarannahr and Turks started to come to positions of power eventually they established their own states. With the emergence of a Turkic ruling group in the region, other Turkic tribes began to migrate to Mawarannahr.>
The first of the Turkic states in the region was the Ghaznavid Empire, established in the last years of the tenth century. Their dominance was curtailed, however, when large-scale Turkic migrations brought in two new groups of Turks in the east the Qarakhanids and the west the Seljuks who conquered the Ghaznavid territory of Khorazm (also spelled Khorezm and Khwarazm).>
In the late twelfth century the Turkic leader of Khorazm united Khorazm, Mawarannahr, and Iran under his rule. Khorazmshah Kutbeddin Muhammad and his son, Muhammad II, Mawarannahr continued to be prosperous and rich. However, a new incursion of nomads from the north soon changed this situation. This time the invader was Genghis (Genghis) Khan with his Mongol armies.The Mongol invasion of Central Asia is one of the turning points in the history of the region leaving imprints that were still discernible in the early twentieth century.>