It picks up where the film Restrepo (2010) left off, taking the viewer deeper into the experiences of the soldiers of Second Platoon, Battle Company, 2nd Battalion, 503rd Infantry Regiment, 173rd Airborne Brigade Combat Team of the U.S. Army while they were stationed in Korengal Valley of Kunar Province, in eastern Afghanistan in 2007-8.

The film is composed primarily of footage shot by photojournalist Tim Hetherington and journalist Sebastian Junger in 2007 and 2008 during approximately 10 months spent with Second Platoon, Battle Company, 2nd Battalion, 503rd Infantry Regiment, 173rd Airborne Brigade Combat Team of the U.S. Army at Outpost (OP) Restrepo in Afghanistan's Korengal Valley,[2] along with interviews recorded with some of the soldiers after Second Platoon returned to the 173rd Airborne Brigade Combat Team's base near Vicenza, Italy.

Heatherington and Junger had already assembled the Academy Award-nominated 2010 documentary Restrepo from the same material, but after that film was completed there was still a considerable amount of footage left unused.

Hetherington was killed by shrapnel in April 2011 while reporting on the First Libyan Civil War, so Junger made Korengal as the sole director.

[7] In his review of the film, Justin Chang of Variety wrote that "Sebastian Junger delivers a worthy companion piece to Restrepo with this more reflective dispatch from the front lines of Afghanistan.

Ed Gonzalez of Slant Magazine, for example, called the film "an alternately gripping and dully meandering patchwork of these soldiers' simultaneously chill and quite literally maddening stay in the Korengal that pointedly shuns big-picture philosophizing.