But the "long war" is not so much a traditional conflict with discrete battles composing continuous, identifiable "campaigns. It is a long-term strategic challenge that will demand all elements of U.S. statecraft. From this perspective, Gates' tenure will be judged by history not just by how the Defense Department's leadership copes with radical Islam, but by its performance in five "long wars" that will dominate America's future security landscape.

The fight against violent jihadists will continue, although we must be careful not to see Iraq as the prototype of how it should or will be waged. The future battlefield extends far beyond both Iraq and Afghanistan to the Muslim world at large, including Islamic diaspora communities in Europe that are growing and becoming increasingly radicalized. Unlike the war in Iraq, the military role in this campaign will shift to more of a support role.

In Asia, the United States faces a China that is growing in both power and self-confidence. While the status of Taiwan remains a trigger point between Washington and Beijing, security competition between the two powers is real and growing. Managing the frictions that will arise will require strategic acumen and agility, sustained over a generation or longer.

The ongoing crises with Iran and North Korea highlight the third "long war" confronting America's strategists: dealing with militarily weak regional powers that covet nuclear weapons as the ultimate deterrent to regime failure or overthrow. The U.S. military has paid too little attention to this thorny problem. These are adversaries that, if and when they possess nuclear weapons, may be prone to use them if they see a confrontation with the United States as a threat to their survival. The challenge: how to project power in defense of U.S. and American allies' interests without sparking a nuclear war.

The fourth profound challenge is that posed by the wayward direction of President Vladimir Putin's Russia. Moscow's weakness over the past decade allowed the West to ignore the failure of hoped-for liberalization in Russia. Today, we see a country with an economy buttressed by high oil prices while its political system becomes increasingly centralized, corrupt and authoritarian. In addition, Russian society is suffering from population losses the likes of which the industrial world has never seen.

Although it would certainly be premature to predict that a new "cold war" is imminent, Russia today is once again staking its claim to a prominent position on the global stage, but with a script out of sync with America's interests.

Finally, the United States must confront these challenges at a time when its network of alliances and partnerships is changing and, in many instances, fraying. Although the war in Iraq has had an effect, changes in the world at large -- many underway well before Sept. 11, 2001 -- are driving even long-time friends to reassess the shifting mix of risks and rewards in their dealings with the United States.

The rise of China, India and Japan as newly assertive great powers is remaking the geo-strategic landscape in complex and unpredictable ways and, in turn, is refashioning U.S. relationships throughout Asia. NATO is playing a high-stakes game in Afghanistan, one in which the international security organization's very future may depend on the performance of the few thousand troops it has deployed there. And, of course, America's role in the greater Middle East is being reshaped by the force of events in Iraq and -- to a lesser but crucial extent -- in Iran, Lebanon and the Palestinian territories.

These five fundamental strategic challenges would represent a full plate for the Department of Defense even without the traumatic effects of the war in Iraq. It may be that the first decades of the 21st century will prove to be among the most trying in America's history.

Gates cannot be expected to "win" any of these wars, but he can and should ensure that the Department of Defense begins to address each of them. Meeting these challenges will be difficult, painful and costly. But failing to do so will only result in worse problems in the future.

(Andrew R. Hoehn is the vice president and director of Rand Project Air Force and David A. Shlapak is the acting director for strategy and doctrine for Rand Project Air Force at the Rand Corp., a nonprofit research organization.)

(United Press International's "Outside View" commentaries are written by outside contributors who specialize in a variety of important issues. The views expressed do not necessarily reflect those of United Press International. In the interests of creating an open forum, original submissions are invited.)

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