Why the war between Afghanistan and Pakistan shows no sign of ending

Torkham, Afghanistan: As the sun sets, the sound of gunfire, mortar and airstrikes reverberates across the towering mountains that straddle the rugged border between Afghanistan and Pakistan — two sister nations now engaged in deadly clashes.
While the world is focused on the spiraling war with Iran, another conflict is raging on Iran’s doorstep. Civilian deaths are rising and the fighting between two intertwined neighbors shows no signs of easing.