The Battle of Qatwan took place very, very far from the Holy Land, so it didn’t appear to have a direct connection at first. But it was the beginning of the end for the Seljuk Empire, which had been ruling in Baghdad. Its progenitor, an Oghuz/Turkmen named Seljuk, had converted to Islam around 985, and his descendants moved across Iran until in 1040, they wrested the Central Asian territory from the Ghaznid emperor. From 1055, they were in de facto control of Baghdad.
The Khitans were a large ethnic group in northeast China. They founded the Liao Dynasty in Inner Mongolia and began writing their language in a unique script copied from Chinese. By 1050, they were using Chinese court dress and many began to speak Han Chinese. But they were forced out, northward, by incoming Jurchen, now called Manchu—for whom Manchuria is named. Their king, Yelu Dashi, began striking out in all directions, trying to regain his old territory and expand into new. His tribe was the Kara (Black) Khitans.
The Kara Khitans had never lost their Mongolian-ish customs, so they blended back into Mongolia, in Genghis Khan’s later heartland on the Orkhon River. They began to push westward into the Trans-Oxiania region that had been the farthest reach of the Muslim Conquest. Taking land in modern Kyrgyzstan, they moved into the Fergana Valley, modern Uzbekistan. As they went, they took in more tribal forces, and more.
The Kara Khitans were now in range of Samarkand, last outpost of the Muslim realm. Although the Seljuk Sultan was far away in Baghdad, his son ruled in Nishapur, Iran. He came with an army to the relief of Samarkand.
The Kara Khitai defeated the Seljuk army at Qatwan, 12 kilometers from Samarkand. The Kara Khitan “Western Liao Emperor” Yelu Dashi spent three months in Samarkand, receiving tribute and oaths of loyalty.
Between the battle in 1141 and the Seljuk emir’s death in 1157, the Seljuks’ imperial rule fell apart. They remained as rulers of Azerbaijan and parts of Iran, while Turkmen tribesmen overran Khorasan. Their weakened state allowed independent Turkish lords, like Zengi, to consolidate control in the west. In a distant way, the fall of the Seljuks at the Battle of Qatwan led to the fall of the Crusader kingdoms far to the west.