The foreign policy of the Mongol Empire could be expressed in a single sentence: “If you surrender and pay us tribute, we will spare you; if you fight us, we will wipe you out.” In the thirteenth century, the Mongols became Islam’s worst nightmare.
After the sack of Constantinople by the crusaders in 1204, the military power and prestige of the Byzantine Emperors was finished. The Seljuk Sultans of Konya were now in a position to capture the Byzantine Empire. Had they made a daring military move, they could have captured Constantinople. They failed to take full advantage of Byzantine weakness, but they captured some important Byzantine ports, particularly the city of Alanya on the Mediterranean Sea, and the city of Sinop on the Black Sea.
When Kaykhusraw II became the Sultan of Konya in 1237, he received messages from Mongolia that the Mongol Great Khan wanted him to come to his court to pay homage and accept the position of Mongol Darughachi (governor). Kaykhusraw refused. In June 1243, a Mongol army led by Mongol General Baiju Noyan smashed into the Seljuk Empire and captured the city of Erzurum. Baiju’s intention was to provoke a decisive battle with the Seljuk army. Kaykhusraw had no alternative except facing the Mongols in the battlefield.
The battle between the Mongols and the Seljuk Turks was fought at the defile of Köse Dağ (in modern Northeastern Turkey) on June 26. The Mongol army was about half the size of the Seljuk army. Immediately after the first round of skirmishing, the Mongols pretended to retreat. The Seljuk forces thought that the Mongols were fleeing. They broke formation and rushed to chase the enemy. After retreating for a short distance, the Mongols circled back and surrounded the disorganized Seljuk army and started slaughtering them.
Kaykhusraw realized that his army was defeated, and he left the battlefield with his commanders. Most of their soldiers fled from the battlefield. The Mongols took control of the cities of Sivas and Kayseri. Kaykhusraw fled to Antalya. Eventually he paid a significant tribute to Baiju and became a vassal of the Mongol Great Khan.
On their way to Asia Minor from Mongolia, the Mongol army had attacked several Turkish settlements and they had forced the Turkish tribes to flee to Asia Minor. Tens of thousands of Turks had poured into Asia Minor before the Mongols. They refused to go back to their homeland. They were adamant about practicing their tribal customs. It was difficult to control them and align them to the Islamic way of life. In the wake of defeat by the Mongols, the Sultans of Konya could not muster the resources to assimilate these migrants from Central Asia. The pressure of the migrants, led to the disintegration of the Seljuk Empire into a number of principalities.
Ironically, by defeating the Sultans of Konya, the Mongols helped in the spread of Islam. Among the Turks that they drove into Asia Minor, there were theologians, mystics, artists, craftsmen, and merchants who contributed in the propagation of Islam. Jalal ad-Din Rumi was among Turks who fled to Asia Minor with his family during this period. Rumi would eventually start the Sufi movement which would inspire many Christians to adopt Islam.
The other consequence of the decline of the Sultans of Konya was that the space was cleared for the rise of the Ottomans. Osman Ghazi, who founded the Ottoman Empire, was a minor chieftain (Bey) of the Sultans of Konya. In the final decades of the thirteenth century, no one could have believed that his successors would one day forge an empire that would control much of Southeastern Europe, Western Asia, and Northern Africa. He was able to build a formidable army by incorporating the Turks who had arrived in wake of the Mongol invasion. In 1302, he gave a demonstration of his military strength by defeating the Byzantines in the Battle of Bapheus.
Osman’s successor, Orhan Ghazi, became the Bey in 1326. In the same year, he captured the city of Bursa from the Byzantine Empire. In 1337, he took the title of Sultan (the word means guardian) and made Bursa the first Ottoman capital. In 1354, the Ottomans marched into Europe and conquered the Balkans. They conquered Constantinople in 1453.