 Complete the following phrase:  Sher Shah instituted a policy of populating the region from Nilab to Lahore with Afghans from Roh. Next he launched campaigns against the Gakkhars, about whom he suspected of being friendly with the Mughals. During this period, Sher Shah constructed the Rohtas Fort near Jhelum. Following the death of Sher Shahs successor, Islam Shah. In 1556, the Sur Empire fragmented into four separate and hostile divisions. The Punjab region came under the control of Sikandar Suri who also controlled Delhi and Agra. However Mughal forces under Humayun defeated Sikandar at the 