The Red Fort and the city of Shahjahanabad was constructed by the Emperor Shah Jahan in 1639 A.D. The layout of the Red Fort was organised to retain and integrate this site with the Salimgarh Fort. The fortress palace is an important focal point of the medieval city of Shahjahanabad. The planning and aesthetics of the Red Fort represent the zenith of Mughal creativity which prevailed during the reign of Emperor Shahjahan. This Fort has had many developments added on after its construction by Emperor Shahjahan. The significant phases of development were under Aurangzeb and later Mughal rulers. Important physical changes were carried out in the overall settings of the site after the First War of Independence during British Rule in 1857. After Independence, the site experienced a few changes in terms of addition/alteration to the structures. During the British period the Fort was mainly used as a cantonment and even after Independence, a significant part of the Fort remained under the control of the Army till the year 2003.
The Red Fort was the palace for Mughal Emperor Shah Jahan's new capital, Shahjahanabad, the seventh Muslim city in the Delhi site. He moved his capital from Agra in a move designed to bring prestige to his reign, and to provide ample opportunity to apply his ambitious building schemes and interests.
The fort lies along the Yamuna River, which fed the moats that surround most of the wall. The wall at its north-eastern corner is adjacent to an older fort, the Salimgarh Fort, a defense built by Islam Shah Suri in 1546. Construction on the Red Fort began in 1638 and was complete by 1648. However, it is believed that it is the ancient city of Lal Kot which was captured by Shah Jahan since Lal Kot literally means Red (Lal) Fort (Kot). Lal Kot was the capital city of Prithviraj Chauhan in the late 12th century.
On 11 March 1783, Sikhs entered Red Fort in Delhi and occupied the Diwan-i-Am. The city was essentially surrendered by the Mughal wazir in cahoots with his Sikh Allies. This task was carried out under the command of the Sardar Baghel Singh Dhaliwal of the Karor Singhia misl.
(Sardar Baghel Singh Dhaliwal on the third of his 3 campaigns to conquer Delhi.)
The Red Fort stands at the eastern edge of Shahjahanabad, and gets its name from the massive wall of red sandstone that defines its four sides. The wall is 1.5 miles (2.5 km) long, and varies in height from 60ft (16m) on the river side to 110 ft (33 m) towards the city. Measurements have shown that the plan was generated using a square grid of 82 m.
The Red Fort was conceived as a whole, and subsequent modifications have not taken away from the overall unity of the scheme. In the 18th century, however, occupiers and looters damaged some sections of the palace. After the Sepoy Mutiny of 1857, when the Fort was used as a headquarters, the British army occupied and destroyed about four-fifths of its pavilions and gardens. A program for restoring the surviving parts of the fort began in 1903.