A Hesco is a giant basket made of wire and lined with heavy fabric, a cube eight feet on a side that can hold 25 tons of rock or sand. A line of Hescos makes a barrier that can dam floodwaters or protect a military base. The men of Second Platoon carve their Restrepo outpost from a hillside and pour the rock debris into a wall of Hescos that shields them during attacks by Taliban insurgents.

Hooch is military slang for a hutch or hut, usually made from plywood or other light materials and used as living quarters or for storage. At the Restrepo outpost, the men build plywood hooches. The huts’ sizes and shapes vary depending on their location on the roughly carved-out hillside lot.

One of five valleys in the rugged foothills of the Hindu Kush mountain range in eastern Afghanistan, Korengal is where First and Second Platoons of Battle Company are stationed. Their job is to stop enemy fighters, weapons, and ammo smuggled in from Pakistan. The valleys are scenic but supremely hard to control given the rugged terrain, often-harsh weather, and uncooperative inhabitants.

The valley’s culture is religious and conservative. American attempts to improve the locals’ lives are often rejected for complex social and political reasons.