Bakhtiyar Khalji inaugurated Muslim rule in Bengal by conquering Nadia in early 1205 AD. A native of Garamsir (modern Dasht-i-Marg) in northern Afghanistan, Ikhtiyaruddin Muhammad Bakhtiyar Khalji belonged to the Khalji tribe of the Turks. He entreated Muhammad Ghuri at Ghazni to enlist him as a soldier but, because of his short physical stature with long arms extending below the knees, his prayer was rejected. A dejected Bakhtiyar proceeded to Delhi and sought an employment under Qutbuddin but there also his fate fared no better. Thence he went to Badaun where Malik Hizbaruddin appointed him to a lower post. From Badaun he repaired to Oudh and got a post befitting his ability under Malik Hushamuddin, the governor of the province. He was granted the parganas of Bhagwat and Bhiuli in the district of Mirzapur as jagir. Soon a large number of Khalji adventurers gathered around him and with their help he carried on raids into the neighboring Hindu territories and the amount of his soldiers increased gradually as well.
In 1203 AD Bakhtiyar made a sudden dash against Bihar, occupied it, destroyed Odantapur Bihar and returned with enormous booty. He met Qutbuddin Aibak and gave him valuable gifts. Qutbuddin in turn received him with great honour. Turning now his attention towards Bengal Bakhtiyar started on his adventure in the winter of 1204 AD and, proceeding through the unfrequented Jharkhand region, marched towards Nadia that only eighteen horsemen could keep pace with him. The city dwellers took him to be a horse-dealer and he captured the palace by surprise. Raja laksmanasena 'fled away by the back-door'. Meanwhile the main army of Bakhtiyar Khalji arrived and nadia came under Muslims possession.
Bakhtiyar Khalji stayed in Nadia for a short period and then marched upon Gaur (lakhnauti). He conquered it without any resistance in 601 AH/1205 AD and made it the Capital of his government. Afterwards he proceeded eastward and extended his authority over north Bengal. Bakhtiyar Khalji's territories extended from the modern town of Purnia via Devkot (in Dinajpur) to the town of Rangpur in the north, to the river Padma in the south, to the rivers Tista and Karatoa in the east and to the previously captured territory of Bihar in the west.
The last important event in the career of Bakhtiyar Khalji was his Tibet expedition. Bakhtiyar collected necessary information about the routes leading to Tibet by sending there a few detachments. Ali Mech, a Mech trivial, agreed to act as his guide through the hills. Before undertaking his Tibet expedition Bakhtiyar made adequate arrangements for the defense and administration of his kingdom. He created three big frontier governorships and posted shiran khalji, alimardan khalji and husamuddin iwaz khalji at Lakhnur, Ghoraghat and tandah respectively.
Bakhtiyar Khalji marched from Devkot with ten thousand horsemen up the river Begmati in early 602 AH/1206 AD. Crossing the river over an ancient stone bridge he proceeded to the hills where, in a battle with the local people, he sustained heavy losses and decided to abandon the project. But the backlash was so hard that the return journey proved to be disastrous and he somehow reached Devkot with a little more than a hundred of his followers alive. At Devkot, Bakhtiyar Khalji fell seriously ill and he died. According to minhaj-i-siraj that, he was stabbed to death by Ali Mardan Khalji in 602 AH/1206 AD.
Bakhtiyar was a good administrator. He divided the kingdom into a number of districts and assigned them to the care of his principal nobles and military chiefs. They were entrusted with the duty of maintaining peace and order, collecting revenues, patronising learning and culture and looking after the moral and material well being of the people. He took steps to read the Khutbah (verses of the Quran) and introduce coins in the name of his lord Sultan Muhammad Ghuri. He built a new capital on the site of Gaur and established two cantonment towns near Dinajpur and Rangpur. He named his administrative divisions iqta and the governor of an iqta was designated as muqta. He built numerous mosques, madrasahs and khanqahs. [ABM Shamsuddin Ahmed]