According to a Firman by Ahmad Shah Bahadur Hafiz Rahmat Khan was assigned to support Feroze Jung III against the Mughal Grand Vizier Safdarjung, who was defeated and forgiven and thus withdrew to become just the Nawab of Awadh and died in 1753.
When Ahmad Shah Bahadur tried to have young Feroze Jung III removed from the imperial court, the outcast then sought an alliance with the detested Maratha chieftain Sadashivrao Bhau.
Since then Hafiz Rahmat Khan entered the service of Najib-ul-Daula and constantly fought the Marathas led by Sadashivrao Bhau and opposed Feroze Jung III.
He played an important part in Indian warfare over several decades, being on the winning side of Afghans at the Third Battle of Panipat of 1761, but was defeated and killed in the Rohilla War.
When the demand was refused the Nawab joined with the British under Governor Warren Hastings and his Commander-in-Chief, Alexander Champion, to invade Rohilkhand and Hafiz Rahmat Khan Barech was killed in the ensuing Battle of Miranpur Katra in 1774.