The American helicopter rides high above eastern Afghanistan, through a pass in the towering Hindu Kush range.

NPR: Commanders Look For New Strategy In Afghanistan

Between mountains in the Hindu Kush range lie six, sky-blue lakes.

NPR: Amid War, Afghanistan Builds Its First National Park

Bullard pointed to a primary geographical challenge: the Hindu Kush mountain range that bisects the country, roughly separating north from south.

WSJ: U.S. Sets Stage for Exodus from Afghanistan

American officials admit that Afghan forces don't have the ability to patrol the entire border, which cuts through the Hindu Kush mountain range, whose peaks exceed 20, 000 feet.

WSJ: Role Reversal: Pakistan Fears

But whereas the base in the Korangal was situated about halfway up a mountainside, in a former lumberyard, the one in Kamdesh would sit in a cup within the valley's deepest cleft, ringed by three steep mountains that formed part of the 500-mile-long Hindu Kush mountain range.

CNN: Excerpt: 'The Outpost: An Untold Story of American Valor'