N.B.: This is a story I've been mulling over for a while. It may be incendiary to place responsibility at the feet of the Bush Administration, but I think there is justification for it.
Since the end of the Cold War, the United States military has contracted in size. Our military budget is larger than the entire working budgets of most countries, to be sure, but our high-tech military has high front-end costs, not just actual equipment, but R&D. I perused the 2011 DoD budget numbers the other day (the declassified portion, over 800 pages, is in multiple .pdf form) prepping for this post, and taking the position that budgets are a good indication of priorities and underlying assumptions, I got the sense that, for all the complaining so many do about the size and scope of the military budget, it reflects the general consensus of the past 20 years that a highly technical, well-trained military can be lean and effective.
Unfortunately, since the end of the Cold War, all Presidents have seen fit to use the United States military as an easy fall-back tool to achieve certain foreign policy goals. Even as the Berlin Wall was being dismantled and chuncks of concrete were being auctioned off, the US decided that an invasion of Panama was a nice short-cut to ridding itself of the thorn of Manuel Noriega. Desert Storm/Desert Shield followed the next year. Finally, as lame-duck, George H. W. Bush committed forces to Somalia. Clinton had to deal with that, plus Haiti, plus policing various Balkan truces and peace accords. There was the bombing campaign in Kosovo, which managed to achieve very little. All the while, the United States Air Force policed the No-Fly Zones established in Iraq after the first Gulf War, plus conducted a couple serious bombing raids. We lobbed cruise missiles at Al Qaeda targets after the bombings of our embassies in Kenya and Tanzania. The Navy has done a couple exercises as warnings to China, always a dangerous game. Afghanistan. Iraq, again.
This list doesn't include those deployments that were considered or demanded or otherwise part of our public debate and discussion. Right after the Rwandan genocide, there were calls for the US to send troops too police the peace there (even though the Canadian military that were present as part of a UN peacekeeping effort, castrated by UN ROE, were forced to stand by and do nothing even as the slaughter was under way). We constantly read that we "need" to send troops to Sudan to police the Darfur region. There is, under current Security Council Resolutions at the UN, good reason to send troops to Western Sahara (the African Union and I think a couple European countries are there now), enforcing Resolutions to keep Morocco at bay there.
Have I mentioned that the US nearly went to war a couple times with North Korea in the past 20 years, with 35,000 American troops on the firing line there?
So, we had this rather promiscuous use of our military, on the one hand, even as the number of persons in uniform actually shrank. We kept demanding that the service chiefs do more with less. This was raised to absurd proportions with the Iraq invasion. We invaded with about half the troops the service chiefs recommended, mostly to do police-work after the war was won. Rumsfeld's infamous dig, "You go to war with the military you have, not the military you want," was a signal to anyone who was listening that he, and his superiors (Bush and Cheney) held the services in contempt.
The gap between what was needed for occupation duty and what was available was made up in a few ways - calling up the reserves, multiple rotations in and out of combat/occupation zones, and the ready-reserve (recalling to active duty retired service members). There was a truncated debate over reinstituting a draft; Charlie Rangel, a Korean War veteran, made some speeches on the House floor, but members of the Bush Administration and Joint Chiefs balked. This debate left unaddressed the whole issue of force size in a time when the US, for all intents and purposes, was (and is) fighting a war on multiple fronts (there are two major fronts, Iraq and Afghanistan; there are troops facing combat conditions in various ways in the Philippines, Yemen, and other places as well which we probably don't know about).
The cost on our military personnel has been high. The services have been playing catch-up on addressing the issue of the emotional cost of demanding so much from so few, and they are doing more. All the same, along with suicide, we have the rise of social dysfunction among veterans - crime and various substance abuse issues, domestic violence and criminal activity in general.
In 2000, then-candidate George W. Bush was correct, to an extent, in criticizing Pres. Clinton for overextending the US military, both in terms of commitments and military action. After the September 11 attacks, when it was pretty clear there was to be a military response, Pres. Bush had the perfect opportunity to address the issue of "overextension"; the public was ready for a call to service, to be sure. Instead, we had the marvelous combination of bureaucratic parsimony and policy profligacy. And tax cuts, too.
You reap what you sow, I guess. There may well be blame to go around to all sorts of actors. All the same, going to war and carrying out an occupation on the cheap has extracted a terrible cost on our troops, one that we will be paying for years unless addressed now.