The Pashtun tribes inhabiting the border areas were divided between what have become two nations ; Afghanistan never accepted the still - porous border .
Clashes broke out in the 1950s and 1960s between Afghanistan and Pakistan over the issue .
The Pashtun tribes inhabiting the border areas were divided between what have become two nations ; Afghanistan never accepted the still - porous border and clashes broke out in the 1950s and 1960s between Afghanistan and Pakistan over the issue .