Outub-ud-din Aibak attacked the pride of the Chandella dynasty and seized the Kalinjar fort, Bundelkhand in the year 1202 A.D during the reign of Parmardi. Parmardi fought with bravery against the Muslims but he failed. Parmardi's dewan Ajaideva was not in favour of submitting their territory to the enemy and he continued the war after the death of Parmardi. But he was compelled to submit because of lack of water in the fort. Thus, Kalinjar was conquered by the Muslims.

Scholars are of the view that after the battle Muslims plundered the treasury of the fort. About 50,000 Hindus were made slaves. Many temples ware broken and Hindus were forcibly converted to Islam. Bakhtiyar appointed Turks and Khiljis to governorship of various parts of Bengal and other parts of India also. Ali Mardan, Muhammad Shiran, Hisham-ud-din Iwaz were chieftains to rule under the flag of Delhi Sultanate. He established many mosques and madrasas, destroyed many Hindu temples and Buddhist and the Janise monasteries. Not only had that he converted many Hindus to Muslim.

After his death, Ijjuddin Muhammad Shiran Khilji captured Ali Mardan, and declared himself the successor. After that he escaped and complained to Qutb-ud-din Aibak, who was ruling Delhi as a governor of the Ghoris. Qutb-ud-din Aibak sent Kayemaz Rumi from Lucknow to help, he appionted Hisham-ud-din Iwaz as ruler from Devkot, who handed over control to Ali Mardan when he was appointed by Qutb-ud-din in around 1210 AD.

The loss of Kalinjar and Mahoba gave a fatal blow to the Chandella dynasty. According to Dr. V. A. Smith, "During the five and a half centuries, in between the death of Harshavardhana and the Mohammadan conquest the countless Hindu states which took shape from time to time varying continually in number, extent and their relations, one with the other, seldom were at peace."

The rise of Qutb-ud-Din Aibak aroused the jealousy of Taj-ud-Din Yildoz of Ghazni. Aibak charged him with exercising undue influence on Mahmud of Feroz Koh and marched against him. In 1208, he even occupied Ghazni and also won over Sultan Mahmud to his own side. He also secured from him a letter of caution along with the paraphernalia of royalty or chatter and Durbesh and also authority to rule over Ghazni and Hindustan. However, Aibak was driven out of Ghazni by Yildoz. Aibak came back to Lahore.

Conquest in Bengal
So far as Bengal and Bihar were concerned, the death of Ikhtivar-ud-Din Khalji threatened to break the relation of Delhi with Bengal and Bihar. Ali Mardan Khan declared himself independent of Lakhnauti, but the local Khalji Chiefs replaced him by Muhammad Sheran and threw him into prison. However, Ali Mardan Khan managed to escape from jail and went to Delhi. He also persuaded Aibak to intervene into the affairs of Bengal. The Khaljis agreed to recognise Aibak as their overlord. They also agreed to send the annual tribute to Delhi. On account of his being otherwise very busy, Aibak could not follow a policy of aggression against the Rajputs. Aibak was a great military leader. He won a large number of victories in battlefields during the lifetime of his master and thereby added to his glory. He rarely lost a battle. According to Minhaj-i-Siraj, Aibak was a "high-spirited and open hearted monarch. He was very generous." "His gems were bestowed by hundreds and thousands."

Administration of Qutub-ud-din Aibak
Aibak was so much busy otherwise that he did not find time to establish a sound system of administration in the country. The whole thing was based on the military. He kept garrisons not only at the capital but also in all important towns of his kingdom. The local administration was left in the hands of the people of the country. Muslim officers were merely put in charge of various departments and most of them were soldiers. The administration of justice must have been crude. It is too much to say that during his reign "wolf and the sheep drank water out of the same pond." It is also not correct to say that Aibak was kind to the Hindus as there is evidence to show that during his wars against Anhilwara and Kalinjar, the Hindus were enslaved and converted and mosques were built on the ruins of the Hindu Temples. However, in times of peace Aibak was really tolerant

Aibak died in 1210 on account of injuries received as a result of fall from his horse while playing polo. According to some scholars, Aibak is not considered to be an independent Sultan of India. We have not come across any coin of Aibak. It is possible that he may not have struck any coin in his name.