Wartime supply demands for the U.S. Army are costing more than anyone anticipated. As in past wars, the army quickly adapted to unforeseen combat conditions. In every war, there are lots of unforeseen conditions. No one has yet found a way to get around that. But the solution has been expensive. Consider the cost of the gear a soldier wears into combat. Before September 11, 2001, if was about $8,000. Now it's $25,000. The additional money went to new, and more effective, armor, better first aid gear, personal radios and new uniforms. All this saves lives, resulting in American troops having the lowest casualty rates in modern history, rates that are about a third of those suffered by troops who fought in Vietnam. But it costs money, especially for the extensive medical facilities waiting for the dozen or so casualties that occur each day.
But the biggest additional expenses have been base building, base maintenance, and transportation. Since Vietnam, the army has learned that it's wise to do all you can to maintain troop morale. All these guys and gals are volunteers. They can be remarkably effective, if you treat them right. That means really tight security for American bases in Iraq and Afghanistan. There have been only a few casualties in those bases as a result of billions spent on building and equipping them. New electronic surveillance equipment does wonders to spot terrorists trying to get in, but this stuff is expensive. The bases have air conditioning for most of the troops living quarters. This was a smart move, because trying to sleep in all that heat is rough for Americans coming in from a life where comfortable sleeping quarters are the norm. The food and other amenities are excellent. While combat troops may spend days at a time "outside the wire" (off base), roughing it, they know that when they get back to base, they can catch a shower, unwind with some video games, and sleep in cool comfort. All this makes a big difference in troop effectiveness, but it costs money.
Another major expense was protecting the trucks that brought in all the supplies (especially water and fuel) to those bases. A basic hummer, that cost $33,000 in 2001, now costs over $200,000 in Iraq, tricked out with armor and electronics (jammers to defeat IEDs). Armor kits for larger trucks can cost up to $100,000 per vehicle.
Training costs have gone up, because it quickly became clear that, in wartime, troops needed more practice with their weapons, and real ammunition. That, along with pay raises (mainly linked to inflation), raised the cost per solider per year from $75,000 in 2001, to over $120,000 today. The Department of Defense is buying over a billion rounds of small arms ammunition a year, compared to 250 million 2001. Most of that is used in training, not combat.
Air freight is costing billions of dollars a year, most of being supplied by civilian contractors. This is crucial in Afghanistan, where there are few roads, or railroads.
While a lot of additional money (nearly half a trillion dollars) has been provided for the war on terror, the distribution of that money has changed, in recognition of the fact that the army is doing most of the fighting. But the navy and air force are still getting more of the defense budget, per capita, than the army. That's because the air force and navy use much more expensive weapons (warships and warplanes). The navy and air force are shedding people, and some programs, but because of the long lead time for building ships and aircraft, most of the procurement budget is locked in for years to come. So the army has to scramble for money, despite all the cash being thrown at the war effort.