Charhat Singh Sandhu was grandfather of Maharaja Ranjit Singh. He was eldest of the four Sons of Sardar Naudh singh Sandhu. He took to arms while still very young and started taking part in the raids and expeditions led by his father. He also fought in the Sikh's skirmishes with the Afghan invader Ahmad Shah Durrani. After the death of his father, he broke away from the Faizullapuria Misl and determined to acquire territory for himself. He left his ancestral village of Sukkarchakk and established his headquarters at Gujranwala, where he had gathered a considerable following within a short time.

One of his constant companions was, Amir Singh, who was known in the area for his valour. In 1756, Charhat Singh married Desan, the eldest daughter of Amir Singh. This united the resources of the two families and added considerably to the importance of the young Sukkarchakkia chief. Charhat Singh attakhed Eminabad, killing the faujdar and plundering the town . He next captured Wazirabad. His most significant victory was at Sialkot, where in August 1761 he besieged Ahmad Shah Durrani's general, Nur ud-Din Bamezat. He pressed the Afghan general hard and forced him to flee the town. He had now to face Khwaja Ubaid Khan, the Afghan governor of Lahore, who marched upon Gujranwala to chastise him. The town was besieged, but Charhat Singh fought with courage and surprised the besiegers by his night sallies. In the mean time, other Sikh sardars, under the leader ship of Jassa Singh Ahluvalia, came to his rescue. Ubaid Khan was forced to retreat, leaving behind siege guns, ammunition and stores. In the Vadda Ghallughara or Great Holocaust of 5 February 1762, when the Sikhs were involved in a pitched battle with Ahmad Shah Durrani, Charhat Singh fought with great skill and courage.

No sooner had Ahmad Shah returned to Afghanistan than the Sikhs reappeared all over the Punjab. Charhat Singh and the Bhangi Dhillon sardars sacked Kasur in April 1763. In November 1763 he engaged at Sialkot the Shah's commander-in-chief, Jahan Khan, who had been especially sent to punish the Sikhs, and inflicted upon him a severe defeat. The Shah who came out himself was forced to return home harassed by the pursuing Sikh bands.
Charhat Singh swept across Rachna and Chaj Doabs and reached Rohtas. The Afghan commander of the fort, Sarfaraz Khan, offered stiff resistance, but was overcome near Attock. Charhat Singh defeated Sarbuland Khan, governor of Kashmir, who was on his way to meet the Afghan ruler at Lahore. He followed these victories with the occupation of a large portion of Dhanni and Pothohar areas. He then took Pind Dadan Khan, and built a fort there. The Salt Range of Kheora and Miani was the next to fall to him.

Charhat Singh's rapid successes, especially in the Salt Range and Pind Dadan Khan, aroused the animosity of the Bhangi Dhillon sardars who had always reckoned these areas within their sphere of influence. Their antagonism came into the open when Charhat Singh and the Bhangi sardars took up sides in the family dispute at Jammu. Its ruler, Ranjit Deo, wanted to pass on the succession to his younger son, but was opposed in this attempt by Brij Raj Deo, the elder son, who managed to secure the active support of Charhat Singh and of the Kanhaiyas. Ranjit Deo enlisted the support of the Bhangis. The rival armies marched into Jammu in 1770. Charhat Singh was fatally wounded in the skirmishes that followed the bursting of his own gun.

Excerpts taken from these books.
Encyclopedia of Sikhism by Harbans Singh ji.
Published by Punjabi university, Patiala