The Ghurid Empire reached its greatest extent under two brothers: Ghiyath al-Din Muhammad and his younger sibling Muhammad of Ghor. After expelling the Ghaznavids from their last stronghold in 1186, the Ghurids won a decisive victory at the Second Battle of Tarain in 1192 against the Chahamana king Prithviraja III, opening the Ganges valley to conquest. Muhammad of Ghor and his slave generals pushed east into Bengal. But conquest in India meant distraction from the rivalry closer to home. The Khwarazmian Empire controlled the lands northwest of Khorasan, and when Shah Tekish died in 1200, the Ghurids saw opportunity in the succession crisis that followed.

Tekish's son Alauddin Shah fought his way to the Khwarazmian throne, then tried diplomacy. He wrote to the Ghurids, offered to be treated as a son, and proposed marrying his mother Turkan Khatun to Muhammad of Ghor. The Ghurids rejected every overture. When Ghiyath al-Din died of illness in Herat in 1203, Muhammad became sole ruler and turned his full attention to the Khwarazmians. He drove Alauddin from Merv, defeated him east of his own capital, and then besieged Gurganj itself, aiming to destroy the Khwarazmian Empire entirely. It was overreach. Alauddin sent for help from the Qara Khitai, who dispatched 40,000 soldiers under the commander Tayangu of Talas, joined by the Qarakhanid ruler Uthman ibn Ibrahim of Samarkand.

Faced with a massive relief force approaching from the north, Muhammad abandoned the siege and began retreating toward Ghazna. The Qara Khitai positioned themselves along the Oxus River to intercept him. Alauddin's forces harassed the retreating Ghurids at Saifabad, inflicting heavy losses at Hazar Saf before the combined Khwarazmian and Qara Khitai armies surrounded them. Muhammad led from the rear with 20,000 cavalry. His soldiers, exhausted from the long march south from Gurganj, began breaking. Muhammad himself took an arrow wound and was carried by his slave general Aibak Yogi to a castle between Merv and Balkh. The soldiers who covered his retreat were slaughtered, among them Nasiruddin Aitam, the Ghurid governor of Multan and Uch. The chronicler Hasan Nizami wrote that "only a few persons from the army of Islam were left."

Even the castle offered no safety. The victorious army breached its walls. Only the intervention of Uthman ibn Ibrahim, the Qarakhanid ruler, saved Muhammad's life -- Uthman reportedly did not want "the Sultan of Islam to be captured by the infidels." Muhammad paid an enormous ransom and was allowed to retreat to Ghazna. The humiliation triggered a chain of rebellions. His general Aibak Beg deserted and seized Multan. Hussain Kharmil abandoned him. The Ghurids lost control of most of Khorasan, retaining only Herat and Balkh. Muhammad suppressed the uprisings and ordered a boat bridge built across the Oxus for a revenge invasion, but he never crossed it.

Before Muhammad could avenge Andkhud, a rebellion by the Hindu Khokhars in the Salt Range cut his communications between Lahore and Ghazni, forcing him back to India. He defeated the Khokhars in a hard-fought battle, but on March 15, 1206, while returning along the Indus, Ismaili assassins killed him. His successor Ghiyath al-Din Mahmud was forced to accept Khwarazmian suzerainty. The Khwarazmians expanded to the Indus River, absorbing Ghazni, Kandahar, and Kabul. Their triumph lasted barely a decade. In 1221, Genghis Khan's armies destroyed the Khwarazmian Empire in its turn. The battle on the Oxus at Andkhud had been the first domino -- the defeat that weakened the Ghurids, empowered the Khwarazmians, and left both too fragile to withstand the Mongol storm.