For more than a decade now, U.S. soldiers have been laboring under a sad paradox: even though the United States enjoys unprecedented global military dominance that should cow enemies mightily, it has found itself in constant combat for longer than ever before in its history, and without much to show for it. Of the U.S. military actions in Kosovo, Afghanistan, Iraq, and Libya, only the first can be counted a success.
Assessing this record is a particularly crucial task now, with U.S. defense policy caught between powerful opposing pressures. Frustration with unending war and with strong fiscal constraints has pushed public opinion sharply toward retrenchment. At the same time, frightening challenges in three critical regions are demanding yet more action: Islamic extremists have seized large swaths of territory in Iraq and Syria, Russia has intervened in Ukraine, and China is flexing its muscles in East Asia. Washington faces a choice: Should it leave these endangered areas to their own fates, or double down on intervention to set them right?
In deciding when to expend blood and treasure abroad, U.S. policymakers should learn from the United States’ recent experience of war, but they must take care not to learn the lessons too well. Overconfidence from success can breed failure, and becoming gun-shy from failure can cause paralysis. For example, the U.S. military’s stunningly quick, cheap, and sweeping victory in the 1991 Gulf War raised policymakers’ expectations about what force could accomplish at low cost, causing them to underprepare and overreach when the United States invaded Iraq a second time. In a similar way, most American leaders have drawn too firm a lesson from the wars in Afghanistan and Iraq: never put boots on the ground. With the deployment of regular army units effectively ruled out, U.S. policymakers who still want to use force have been driven to options that involve airpower alone. That approach may make sense in places where the United States wants only to