US troops work the graveyard shift

By day, this tunnel of mesh camouflage and barrier walls is the only cover for U.S. troops patrolling a dangerous combat outpost in northern Afghanistan.

Here at Pirtle-King, a region that sits precariously in the Kunar River Valley, insurgent snipers have all the advantage hiding in the forested mountains on either side.

For the little boy in every soldier, the danger is what keeps them going-- thumbing their noses at the enemy.

(SOUNDBITE) (English) SERGEANT JOSHUA DANISON FROM A COMPANY, 1-12 INFANTRY REGIMENT, SAYING:

"PK is kind of our childhood fortress that we never got when we were kids so it is pretty interesting, the lifestyle is a bit different being on a kind of vampire cycle but it's pretty cool at the same time, we all enjoy it here, yeah it's pretty interesting."

Troops wear full body armour during the day, when attacks are most likely, and try to lay low until the sun goes down.

And then-- the work begins.

Soldiers fill sandbags, reinforce their walls or fix their vehicles-- all by the cover of night.

Slated for closure when the U.S. troops withdraw from region and handover to Afghan forces the battalion commander here expects a smooth transition.

Julie Noce, Reuters