First of all, what does Professor Walt mean when he says that America is the “most powerful nation on earth”? In military terms, it is true that the United States outspends any other country—indeed, it spends ten times more than the next highest spender. But does that military spending translate into military power? To be sure, the United States possesses very sophisticated technology and can attack targets more or less precisely at very long distances. But that is not the same as what Schelling famously called “compellance.” Despite its apparently extensive military resources, it cannot control either Afghanistan or Iraq—two relatively minor “powers” (to use Professor Walt’s terms). So what does it mean to say that the United States is militarily powerful? Perhaps it means, and this is true, that the United States has the same difficulties as other countries. Russia cannot control Chechnya. Israel cannot control the Palestinian territories. India cannot control Kashmir. Military power has become immensely destructive, and, at the same time, global sensibilities about deliberate destruction increasingly inhibit the use of force. Moreover, the spread of easily available lethal, accurate, and easy-to-use conventional weapons has greatly reduced the comparative advantages of sophisticated military technology.
In other words, military forces are much less useable than in earlier eras, and this represents a profound change in global power relations. If we still believe that military power is significant, and as Professor Walt points out, both America’s friends and foes do still believe this, it is only because of the legacy of past victories, especially during World War II. But every time military power is used, that belief gets eroded.