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.<br/> <br />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.<br/> <br />For the little boy in every soldier, the danger is what keeps them going-- thumbing their noses at the enemy.<br/> <br />(SOUNDBITE) (English) SERGEANT JOSHUA DANISON FROM A COMPANY, 1-12 INFANTRY REGIMENT, SAYING:<br/> <br />"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."<br/> <br />Troops wear full body armour during the day, when attacks are most likely, and try to lay low until the sun goes down.<br/> <br />And then-- the work begins.<br/> <br />Soldiers fill sandbags, reinforce their walls or fix their vehicles-- all by the cover of night.<br/> <br />Slated for closure when the U.S. troops withdraw from region and handover to Afghan forces the battalion commander here expects a smooth transition.<br/> <br />Julie Noce, Reuters
