In March 1747, he entered Lahore and proclaimed himself to be the subedar, putting Yahya Khan in prison.
[1][2] However, after Yahya Khan escaped from his captivity, Shah Nawaz Khan turned to Ahmad Shah Abdali for help, who invaded Punjab in 1748.
He was defeated by Ahmad Shah at a battle near Lahore in 1748, and was forced to flee towards Delhi.
After Ahmed Shah's eventual defeat at Manupur in the same year at the hands of Mir Mannu, Shah Nawaz Khan was again appointed governor of Multan to replace Nawab Zahid Khan, a relative of Ahmad Shah, by the Mughal court.
Mir Mannu due to his political rivalry with Shah Nawaz Khan appointed Kaura Mal as the governor instead, and in the ensuing battle Shah Nawaz Khan was killed in 1749.