A sequel with an unusual provenance, “Korengal” is made up of unused footage from a 14-month shoot from 2007-08 that already yielded the 2010 Oscar-nominated documentary “Restrepo.”

“Korengal” is set in the same war in Afghanistan captured in “Restrepo,” as well as in the same patch of mountainous terrain — the gorgeous but deadly Taliban holdout, the Korengal Valley — as the earlier film.

“Korengal” also features the same soldiers that filmmaker Sebastian Junger and the late cameraman Tim Hetherington closely tracked while embedded with the Battle Company of the 173rd Airborne Brigade.

Where the intense “Restrepo” focused on the harrowing experiences of young soldiers facing the mayhem of war every day, “Korengal” is a little more abstract, an overview of the psychological and emotional impact of living through those experiences for a year. If the latter is a less compelling work than “Restrepo,” its reflections are valuable.

Not surprisingly, the fallout from constant warring — embarking on one mission after another, any of which could be a soldier’s last — is full of contradictions. More than one young man looks back on enlisting and wonders what compelled him to feel he had to do it. Another wonders about the moral consequences of having killed the enemy.

Most fascinating is the seemingly unanimous feeling that while deployment in Korengal was hard and heartbreaking, these veterans would do it all again just to stay together, to remain brothers who mutually understand something no on else will ever know.

Tom Keogh: tomwkeogh@yahoo.com