America has a great opportunity to change the world. Will it do it?

The twenty-first century is fundamentally different. For the first time in modern history, the major powers of the day — currently, the United States, Europe, China, Russia, Japan, possibly India — are not engaged in a classic struggle for domination at each other’s expense. There are few contests over territory. For the foreseeable future, war between or among them borders on the highly unlikely and, in some cases, the unthinkable.

There is no fundamental ideological fault line pitting one great power against another in the world, and certainly nothing comparable to the “Communism versus Free World” axis that defined the previous era. Many governments share the view that “new forces,” including terrorism, disease, and the spread of weapons of mass destruction, constitute the greatest threats to security and stability. And all the major powers (as well as virtually all countries, medium and small alike) share a stake in maintaining the stability that provides a necessary context for the economic interactions that benefit everyone.

In addition, the number of countries that can be accurately portrayed as full or near democracies (more than 100) is the highest in history; the same can be said for market economies. All this bodes well, not just for projected levels of human freedom and prosperity, but also for peace, as there is a good deal of scholarship suggesting that mature democracies are less likely to wage war on one another than countries where democracy has not put down deep roots or where it exists not at all.

We do not owe this good fortune to nuclear deterrence, the linchpin of peace between the two dominant powers throughout the Cold War. Although deterrence remains in effect, today’s major powers do not worry actively about each other’s nuclear intentions. More significant is the fact that U.S. strength — particularly military strength — is so pronounced that it discourages any kind of direct aggression from another state. Just as important, and recent intense disagreements over Iraq and other issues notwithstanding, international acceptance or at least tolerance of American power and purpose remains sufficiently high that other powers are not inclined as a matter of reflex to resist what the United States does around the world. None of the other major powers sees the United States as some contemporary version of, say, late-nineteenth-century Germany, a country intent on continental domination and colonial conquest that, as a result, had to be countered.

In history, no single country has ever possessed greater strength, and few countries or empires have enjoyed such advantages over their contemporaries as the United States does today. The United States now spends on the order of $500 billion a year on defense, more than China, Russia, India, Japan, and all of Europe combined. The qualitative advantage of the U.S. military is such that no other country can compete with the mobility, accuracy, and lethality of the U.S. forces. There is no obvious counterbalance: Today’s world is characterized by dramatic American advantage — a decided imbalance of power.

What is more, the United States enjoys the rare luxury of focusing almost all its defense budget abroad — in Europe, Asia, and the broader Middle East. Even allowing for sharply increased spending on homeland security introduced in the wake of 9/11, the United States spends only 10 to 15 percent of its security dollars on what might be described as self-defense against external threats. Historically, major powers have spent a significant portion of their resources fending off powerful, unfriendly neighbors. By contrast, the two immediate neighbors of the United States are its two largest trading partners. There is no significant threat in the Western Hemisphere. Consequently, much of what the United States devotes to national security is available for use elsewhere around the world.

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