As the Mongols, British and Russians have discovered, Afghanistan is no place in which to lightly launch a war.
And as the Obama administration endeavours to come up with some kind of half-dignified exit strategy, this compelling documentary from Sebastian Junger and Tim Hetherington paints an unforgettable and unsettling picture of what life is like for the troops on the ground.
Junger and Hetherington spent more than a year with a US airborne infantry company on a tour of duty in what was then the most dangerous corner of Afghanistan.
In 2007 and 2008, the remote and inaccessible Korangal Valley in northeastern Afghanistan was the scene of some of the fiercest direct engagements between American troops and the Taliban, and the Battle Company were right in the thick of it. Showing exceptional bravery themselves, Junger and Hetherington followed the troops from their Italian base to the thick of battle, and recorded the psychological effects of both combat and bereavement on the mainly very young men. Some of these soldiers are patriots, but most seem like pragmatists in search of a decent living. But there's nothing decent about the life they face in Korangal.
There are many Irish names among the fighters, and one of them, a high-minded captain called Kearney, does his best to win the hearts and minds of the natives with a series of weekly meetings.
The film's title comes from Private Juan Restrepo, an early casualty, and someone the rest of the troops become increasingly sentimental about. Their courage is admirable, but one leaves the cinema wondering whether their sacrifices have made any difference.