This changed significantly with the widespread adoption of gunpowder between the fifteenth and seventeenth centuries, giving rise to renewed imperial power in China and Japan. Cannon capable of breaching fortified walls and ending sieges was the principal weapon. However, once the new artillery was incorporated into imperial forces, there was little incentive to experiment with new military technologies or forms of organization. Any major recruitment overhauls were likely to upset local power structures. With the suppression of nomadic steppe raiders (through the use of muskets) and the relatively limited presence of European merchantmen, there was little external pressure to alter their methods of warfare. The Asian empires also began to experience internal divisions. Competition between local elites over tax revenue burdened populaces, contributing greatly to the collapse of the Mughal Empire in the eighteenth and nineteenth centuries. Population growth also strained farmers and their children, breeding sectarian violence in China in the 1770s.