Emperor Shah Jahan commissioned the fort on 12 May 1639, after deciding to move his capital from Agra to a new city he would call Shahjahanabad. The architect was Ustad Ahmad Lahori, the same mind behind the Taj Mahal. Construction took nine years, concluding on 6 April 1648. The result was an octagonal fortress stretching along the banks of the Yamuna River, its walls rising 33 meters on the city side and 18 meters where they faced the water. Originally adorned in red and white, the sandstone walls gave the fort its enduring name: Lal Qila, the Red Fortress. Inside, pavilions of white marble lined the eastern edge, connected by the Nahr-i-Bihisht, a channel called the "River of Paradise" that carried water through the private apartments, gardens, and the Rang Mahal, the vividly painted Palace of Colors where the emperor's wives and mistresses lived.

The fort's treasures attracted conquerors as relentlessly as its walls were meant to repel them. In 1739, the Persian ruler Nadir Shah invaded Delhi and stripped the fort of its jewels and artwork, carrying off the legendary Peacock Throne. The Marathas took their turn in 1760, melting the silver ceiling of the Diwan-i-Khas -- the Hall of Private Audience -- to fund the defense of Delhi. Jat rulers from Bharatpur captured the fort in 1765 and seized the Mughal throne, which still sits in a palace at Deeg. In 1783, Sikh forces under Jassa Singh Ahluwalia entered Delhi with 40,000 troops and negotiated their withdrawal only after securing permission to build seven gurdwaras in the city. Each successive power left its mark, and each removed something irreplaceable.

After the Indian Rebellion of 1857, the British response was methodical destruction. Eighty percent of the fort's interior structures were demolished. The harem apartments, servants' quarters, and gardens were razed, and stone barracks were erected on top of their foundations. Only the marble buildings along the eastern facade survived, and even those sustained damage. Bahadur Shah Zafar, the last Mughal emperor, who had been proclaimed leader of the rebellion, was tried at the fort and exiled to Rangoon. The Red Fort became a military garrison, its imperial spaces repurposed for colonial administration. It was Lord Curzon, Viceroy from 1899 to 1905, who began reversing the damage, restoring walls and reviving the gardens. When he returned from a summer in England to find his restoration work undone and the garden planted with turnips, his fury was reportedly considerable.

The fort's transformation from colonial garrison to national symbol happened in a single day. On 15 August 1947, Nehru's flag-raising at the Lahori Gate announced Indian independence to a crowd that stretched beyond sight. The ceremony established a tradition that persists: each Independence Day, the Prime Minister speaks from the same ramparts, broadcast live across the country. The fort appears on India's 500-rupee note. Security on Independence Day is extraordinary -- National Security Guard sharpshooters position on nearby high-rises, and the airspace becomes a no-fly zone. In 2003, the Indian Army transferred control to the Archaeological Survey of India, and four new museums opened in 2019 within the colonial-era barracks, dedicated to the 1857 rebellion, the Jallianwala Bagh massacre, Subhas Chandra Bose, and Indian art.

Today the Red Fort is Delhi's largest monument and one of its most visited, drawing thousands each year through the Lahori Gate and into the Chhatta Chowk, the covered bazaar where Mughal-era merchants once sold silks and jewels. The architectural state is uneven. Some pavilions retain their original inlaid marble and floral designs; in others, looters have pried the stonework away. The water channels that once fed fountains and pools are dry. The Moti Masjid, Aurangzeb's private Pearl Mosque of white marble, is visible only through glass windows. And since the late twentieth century, Delhi's air pollution has been darkening the sandstone walls from red to black -- Italian-Indian studies in 2025 confirmed that tarry crusts of particulate matter, nitrogen dioxide, and toxic metals are accumulating on the surface. The Red Fort endures, but it requires constant defense against threats its builders never imagined.