He and his brother Nawab Sayyid Saddullah Khan Bahadur Rohilla of Rohilkhand fought with Ahmed Shah Abdali in the Third Battle Of Panipat, and was granted Shikohabad.

In 1774, during the invasion of Rohilkhand by the united armies of the Vizier Shuja-ud-Daula and the British East India Company, Faizullah Khan led a resistance in which many of the Rohilla's principal chiefs were killed.

He collected the scattered remains of his countrymen; and as he was the eldest surviving son of Ali Mohammed Khan, he seems at length to have been generally acknowledged by his natural subjects the undoubted heir of his father's authority.

[9] Faizullah Khan soon saw the precariousness of the situation that he had found himself in, with Awadh reduced to a puppet state his authority was palpably undermined, therefore he immediately sought to have the treaty ratified and legitimised by the Governor General in council of the East India Company.

During summer times the region often came under security threat from outlaw Rohillas, Sikhs and Gujars who often carried out lightning raids before returning to their base.

[11] General Hibbert, commander of British troops in western Awadh in 1774 addresses the Governor General in Council saying: "Like Marathas they (Sikhs and Gujars) are sudden and rapid... it is therefore necessary to oppose them and check their progress at several fords across the Ganges, the Rohilkhand and the Doab, which at this season of the year are very numerous, and as this cannot be affected by a small body of infantry without the assistance of cavalry, I do not think that a part of those which Faizullah Khan has proposed to retain, can be more advantageously employed there for this purpose"[11] Faizullah Khan sent his forces on several occasions in sight of his commitments to the Lal Dang treaty, these included: 1781 to 1783 proved to be stressful years for Faizullah, the constant strain that the company put him under challenged the existence of the Rampur riyasat.

In November 1782, Rampuri Troops that had been used for the personal aggrandisement of British Officers rebelled against the Awadh army, bringing an end to the arrangement.

This well exceeded the 3000 horse requirement held by the Treaty of Lal Dang and additionally shocked the company's Court of Directors at the injustice of the Demand.

Faizullah Khan finally relented to the immense pressure and agreed to provide 2000 horse along with 1000 infantry, all this would be accompanied with a year's advance in salary to the troops and funding to the British.

[13] Noting that: The British continued their pressure of extracting tribute form Rampur, Warren Hastings sent his close friend William Palmer to Faizullah Khan in June 1783.

Demanding through Palmer that Faizullah Khan should pay a subsidy for the force of 3000 horse and further reimburse Awadh for the defection of Awadhi peasants to Rampur.

Faizullah Khan initially refused, but under further pressure he eventually relented on, paying a lump sum of 15 lakh rupees to the British.