RĀM RAUṆĪ later known as Rāmgaṛh Fort, was a small mud fortress built in April 1748 near Rāmsar, in Amritsar, to provide shelter to scattered Sikh jathās, in Mughal Punjab. Sikh sardārs, along with their bands, assembled at Amritsar on the Baisākhī day of 1748 and set to building a rauṇī or enclosure. According to Ratan Siṅgh Bhaṅgū, Prāchīn Panth Prakāsh, the Sikhs themselves were the masons and carpenters. The structure consisted of an enclosure of mud-walls, with rudimentary watch towers, and a hastily constructed moat around it. The fortress, named after Gurū Rām Dās, the founder of the city of Amritsar, became a rallying point for the Sikh bands against the recurrent onslaughts of the Mughal satraps of Lahore and the Jalandhar Doāb. When the Sikhs assembled at Amritsar to celebrate the Dīvālī festival of 1748, Mu’in ul-Mulk (Mīr Mannū), the severest of the Mughal governors, led out a force against them. He also summoned from Jalandhar Ādīnā Beg who blockaded Rām Rauṇi where nearly 500 Sikhs had taken shelter, the rest hiding themselves in the bushes near Rāmsar. The siege continued for three months, from October to December, and, reduced to extreme straits, Sikhs wrote to Jassā Siṅgh Rāmgaṛhīā, then known as Jassā Siṅgh Ṭhokā (carpenter) who was in the service of Ādīnā Beg, to come to their rescue. Jassā Siṅgh, responding to the appeal of his Sikh brethren, left Ādīnā Beg to join them. The siege was ultimately lifted at the intervention of Dīwān Kauṛā Mall, Mīr Mannū's minister, who had his sympathies with the Sikhs.

         After the death of Mīr Mannū in 1753, the Sikhs rebuilt the fortress. Jassā Siṅgh Rāmgaṛhīā took a leading part in fortifying it. Renamed Rāmgaṛh, it became the base of Sikhs' future operations. In 1758, when Ādīnā Beg became the governor of the Punjab under the Marāṭhās, he let loose a reign of terror in an effort to exterminate the Sikhs. Rāmgaṛh was invested by his deputy, Mīr 'Azīz Bakhshī. The Sikhs were led by warriors such as Jassā Siṅgh Rāmgaṛhīā, Nand Siṅgh Saṅghnia and Jai Siṅgh Kanhaiyā, but they were severely outnumbered. They put up a brave fight, but had to evacuate the fortress in the end. However, not long afterwards, they reassembled at Amritsar. Rāmgaṛh was repaired and regarrisoned, and continued to serve as a bulwark for the defence of the holy city of the Sikhs. The Rāmgaṛhīā misl derived its name from the fortress which its leader, Jassā Siṅgh, had redesigned.