One of the more underrated, and underreported, weapons in Iraq and Afghanistan, has been the night vision equipment. This stuff has been around since the 1960s, when the first light amplification (takes available light from moon or stars and amplifies it) devices reached the troops in Vietnam. With these, you could see at night. But the early devices were hand held, about the size of a small telescope. Useful, but not decisive. Four decades of further development has produced lighter, more powerful equipment. In addition to the original light amplification systems,  there are now even more capable thermal imaging devices, which create a picture based on the temperature of everything. These can see through light fog and mist and, more importantly, most camouflage. 

Iraq and Afghanistan are the first sustained military operations where the current crop of night vision gear has gotten a major workout. New tactics and uses have been discovered, and older ones amplified. For example, one of the major combat chores is raids. Here, the element of surprise is important. And theres nothing more surprising than a bunch of hummers, with lights out, emerging from the darkness. These vehicles are able to move at high speed, with their lights out, because the driver, and the guy sitting next to him, are wearing night vision goggles. When the raiding party arrives at its destination, the troops rapidly dismount and charge into the building they are to search. In total darkness, the raiding party knocks down doors and subdues any armed or hostile people inside, search, make needed arrests and depart, all in darkness. This has a severe psychological impact on the enemy. 

Many gun sights carried by combat troops incorporate night vision technology. The fire control systems of most armored vehicles has night vision, usually thermal imaging. Security cameras, incorporating zoom capability, are also equipped with night vision. These cameras make it nearly impossible for terrorists to get inside American bases. 

The enemy are using night vision devices as well, often for ambushes against American convoys moving at night without lights. Night vision devices have been on the market for decades, and they got a lot cheaper after the Cold War ended and Russia dumped large supplies of inexpensive military grade stuff (which the Russian army could not afford to buy anymore) on the market. You can now buy night vision cameras to attach to the front of your car, and a display that sits on your dashboard, allowing anyone to do a little lights-out night driving. But the military grade American stuff is better, and expensive (up to $10,000, or more, for a set of goggles.) The military stuff has longer range, a sharper image, and weighs less. 

Because nearly all American troops are equipped with night vision devices (as are crews in aircraft and helicopters), the enemy tends to avoid night operations. At least in daytime, everyone has the same degree of vision.