Donald Rumsfeld's tenure as secretary of defense will continue to be marked by his attempt to transform the military into a lighter, nimbler force better able to take advantage of new technology and respond to new threats. Despite (or perhaps because of) the rancor he has generated within the Pentagon, Rumsfeld has managed to shake up a hidebound institution that, if left to its own devices, would probably prefer to endlessly refight the 1991 Gulf War.
The continued fighting in Iraq, however, shows the limits of what he has accomplished. The U.S. military is superb at defeating conventional forces--as its three-week blitzkrieg from Kuwait to Baghdad in the spring of 2003 demonstrated--but not nearly as good at fighting the kind of guerrilla foes it has confronted since. To be sure, many of the current problems in Iraq result from Rumsfeld's failure to send enough troops there and from the precipitous disbandment of the Iraqi military. But they also reveal more fundamental shortcomings in U.S. capabilities for dealing with unconventional threats.
Many policymakers and military officers will no doubt react to the problems in Iraq by trying to eschew this type of conflict in the future. Just as there was an aversion to fighting guerrilla wars after Vietnam (manifested in the Powell Doctrine), there will be a similar backlash after Iraq, no matter how it turns out. Most U.S. soldiers understandably prefer to focus on what they do best: beating conventional foes in the open field.
Unfortunately, the United States cannot determine the nature of its future wars; the enemy has a vote, and the more evident the U.S. inability to deal with guerrilla or terrorist tactics, the more prevalent those tactics will become. There is a limit to how much "smart" weapons can achieve against a shadowy foe. Recall the ineffectual cruise-missile strikes on targets in Sudan and Afghanistan in 1998, which served only to highlight U.S. weakness. Defeating terrorism, as Washington has learned in Afghanistan, requires