After 1716, the Mughal emperor Muhammad Shah began a campaign of genocide against Sikhs through his Governor of Lahore, Abdus Samad Khan. His son and, later, successor, Zakariya Khan Bahadur led a standing army dedicated to eliminating Sikhs, executed Sikhs publicly, and offered monetary rewards for the heads of killed Sikhs. The Sikhs retaliated by killing government functionaries and plundering Mughal posts, arsenals, and treasuries but could not assemble an army. The persecution of the Mughal Empire forced some Sikhs to abandon the outward signs of their faith, but the more sincere had to seek a refuge among the recesses of the hills or in the woods to the south of the Sutlej The Sikhs went into hiding during this period. From 1718-1738, the Sikhs carried out a guerrilla war against the Mughal Empire in the area around the Sivalik Hills. Historian Josepeh Cunningham writes of the period: The Sikhs were scarcely again heard of in history for the period of a generation.