U.S. troops in Afghanistan have discovered that operating in the steep Afghan hills is, literally, a pain in the butt. Often, the only way to come down a steep slope is to slide down it. Given the abundance of rocks and gravel on those slopes, that sliding tends to tear up trousers. You can see where this is going. So the U.S. Army has a crash program to come up with heavier duty trousers for troops operating in those conditions. The simples approach appears to be just adding some tougher fabric to the butt and crotch area. It isn't just torn up trousers. Early on in Afghanistan, it was discovered that the standard combat boots very quickly wore out because of all those rocks, gravel and scrambling up and down hills.

Actually, the problem of uniforms and boots wearing out quickly in combat is nothing new. It's gotten worse in the last century, as infantry tactics rely more on troops crawling, sliding and scrambling about under fire. Unlike training exercises, where no one is trying to kill you, combat encourages troops to move with more determination and vigor, and that is hell on the uniforms. Stuff that would last 6-12 months in peacetime, is often in tatters after only a month or so in combat.