The Chagatai Khanate had been probing India's defenses for years. In 1292, a Mongol force invaded Punjab but its advance guard was defeated and captured by the then-sultan Jalaluddin Khalji. Around 4,000 Mongol soldiers who surrendered converted to Islam and settled in a Delhi suburb called Mughalpura -- a name that stuck. After Alauddin Khalji seized the throne by assassinating his uncle in 1296, the Mongols kept coming. A raiding force under the noyan Kadar struck Punjab in the winter of 1297-98 and was turned back by Alauddin's general Ulugh Khan. A second invasion led by Saldi was defeated by Zafar Khan himself. Each failure only sharpened the Mongols' resolve, and Duwa Khan, ruler of the Chagatai Khanate, decided the third attempt would be different. He sent his own son with a full army, not to plunder but to govern.

The discipline of the march was remarkable. Over six months, the Mongol army crossed the breadth of Central Asia and Afghanistan without destroying the cities or forts along their route -- a deliberate restraint meant to conserve energy for the conquest ahead. Delhi's frontier garrisons at Multan and Samana harassed them at night, but the Mongols avoided full engagements. Alauddin appears to have learned of the invasion only after the Mongols crossed the Indus River, giving him barely one to two weeks to prepare. He set up camp near Siri on the banks of the Yamuna and summoned his officers. His uncle Alaul Mulk, the kotwal of Delhi, urged diplomacy. Alauddin refused. If he showed weakness, he argued, both his people and his warriors would lose respect for him. He left Alaul Mulk in charge of the city with a stark instruction: hand the keys of the palace gates to whoever wins the battle. All gates were sealed except the Badaun Gate, kept open for a possible retreat to the Doab.

Alauddin's strategy was patience. He had issued a strict order: no officer was to move from position without his command, on pain of beheading. He expected reinforcements from the east and knew the Mongols, exhausted from their long march, would soon run short of supplies. But Zafar Khan -- the same general who had already defeated one Mongol invasion -- attacked the left wing under Hijlak without permission. It was exactly the mistake the Mongols wanted. Hijlak's unit feigned retreat, a classic steppe tactic, and Zafar Khan chased them at such speed that his foot soldiers fell behind and even his cavalry struggled to keep pace. After 55 kilometers, he found himself with only 1,000 horsemen, and a Mongol ambush unit of 10,000 under Targhi had closed the gap behind him. There was no way back. Ulugh Khan, who commanded the reinforcement division, did not ride to his aid -- according to the chronicler Hajiuddabir, he bore Zafar Khan an old grudge.

Surrounded and cut off, Zafar Khan consulted his officers. They saw two options: death in battle or punishment from Alauddin for disobedience. They chose to fight. Qutlugh Khwaja offered Zafar Khan surrender and safe passage to Central Asia, promising treatment more honorable than he received at the Delhi court. Zafar Khan refused. According to the chronicler Isami, he and his companions killed 5,000 Mongols while losing 800 of their own. When his force was reduced to 200 men, Zafar Khan's horse was cut down beneath him. He fought on foot, engaged Hijlak in hand-to-hand combat, and was finally killed by an arrow that found a gap in his armor and pierced his heart. His son Diler Khan charged the Mongols as well, forcing the right-wing commander Tamar Bugha to fall back. But the damage was done.

For two days after Zafar Khan's death, the armies faced each other without fighting. Alauddin's officers urged retreat to the safety of Delhi's fortifications, but the sultan refused to yield ground. On the third night, the Mongols broke camp and marched home. The chronicler Barani credited Zafar Khan's ferocity for terrifying the Mongols into retreat. Modern historian Peter Jackson offers a more prosaic explanation: Qutlugh Khwaja was gravely wounded and died on the journey back. Either way, Delhi was saved. But Alauddin could not forgive disobedience. No one at court praised Zafar Khan's bravery. The sultan publicly denounced his recklessness, and the court poet Amir Khusrau omitted Zafar Khan entirely from the official chronicle, the Khazainul Futuh. The general who had fought to the death defending Delhi was written out of Delhi's history -- at least until later chroniclers restored his name. The Mongols invaded India again in 1303, 1305, and 1306, but never conquered the Delhi Sultanate.