The UAV (unmanned aerial vehicle) has become so popular, and widely used in the American armed forces, that the Department of Defense, and the U.S. Army, have set up operations dedicated to their development and operation. The U.S. Army Unmanned Aerial Vehicle Center has been established in Alabama, within the current U.S. Army Aviation Center at Fort Rucker. The army is the largest user of UAVs, with 574 serving overseas in Afghanistan and Iraq, and hundred more used for training and research at twelve bases in the United States. The army is the largest user of UAVs (by number of aircraft), followed by the marines. But the air force is spending the most money on UAVs, mainly the expensive (and effective) Predators and Global Hawks. The air force is also trying to grab control of all Department of Defense UAV work, but this appears to have been defeated by the opposition of all the other services, particularly the army. Because the army is doing most of the fighting in the war on terror, and taking most of the casualties, it has a bit more clout in these Pentagon power scuffles.