The North-West Frontier (present-day Khyber Pakhtunkhwa) region of the British Indian Empire was the most difficult area to conquer in South Asia, strategically and militarily. It remains the western frontier of present-day Pakistan, extending from the Pamir Knot in the north to the Koh-i-Malik Siah in the west, and separating the present-day Pakistani frontier regions of North-West Frontier Province (renamed as Khyber Pakhtunkhwa), Federally Administered Tribal Areas and Balochistan to the east from neighbouring Afghanistan in the west. The borderline between is officially known as the Durand Line and divides Pashtun inhabitants of these provinces from Pashtuns in eastern Afghanistan.