Khan defended Bihar from Maratha attacks. After Nawab Alivardi Khan and his army general Mustafa Khan killed Bhaskar Pandit, the leader of the Maratha raids, Mustafa expected the governorship of Bihar as his reward. When Mustafa was refused this position, he and his Afghan kinsmen revolted. They attacked Munger and laid siege to Patna. Zain ud-Din Ahmed Khan defended Patna and the rebels were crushed by an army led by Alivardi Khan.