U.S. combat troops in Afghanistan are very deliberately avoiding the mistakes the Russians made. A lot of this has to do with combat support. One major problem the Russians had during their 1980s war was keeping their 100,000 troops healthy. Most of the Russian soldiers who served in Afghanistan got sick, often very sick. The Russian troops always had trouble getting clean water, or clean quarters to live in. American troops have always paid more attention to keeping illness down and they have succeeded in Afghanistan. This means more water purification equipment, plus showers and latrines that use clean water and keep the troops clean at the same time. Russian troops also had trouble with the Summer heat and sandstorms in southern Afghanistan. American troops now have air conditioned tents to sleep in, and other air conditioned tents where they eat and have access to the Internet (for email) and short phone calls home. And most Afghans aren't just "used to it." As the Special Forces discovered when their medics began treating their Afghan allies, a lot of Afghans are constantly coming down with one bug or another, and many have just laid down and died up in the hills. American troops are kept healthy and in good physical shape, so that when they do head off for the hills in their helicopters, they hit the ground in much better physical shape than their opponents. Nothing like a good night's sleep to keep you sharp for combat.