This year marks the 50th anniversary of the alliance between South Korea and the United States, but there's been little celebration lately.

In South Korea, anger over the acquittal for homicide of two U.S. servicemen who accidentally ran over two teenage girls with their armored vehicle has sparked anti-American protests in the capital and other cities. Meanwhile, in the United States, some pundits and policy-makers have been wondering out loud why 37,000 U.S. troops remain in a region where that's been relatively peaceful for a half-century.

Speaking as a former Army officer stationed in Korea, I can say this: It would be a grave error to leave South Korea. For one thing, our presence there is a major reason why there has been peace in the region since the end of the Korean War in 1953. If Americans troops left, deep historical animosities and territorial disputes among Russia, China, Japan and the two Koreas would lead to a major arms race for territory and military dominance. This is not something to brush off, considering three of the five nations have nuclear weapons, and, in the case of North Korea, seem willing to use them.

But protecting the peace isn't the only reason the United States is in Korea. We're there to protect the principles of democracy, too. Thanks largely to an American presence in the Asian region, the democracies of South Korea and Taiwan are protected from hostile threats by dictatorships in North Korea and China.

For Japan, the presence of U.S. forces allows this key ally to maintain its "peace" constitution, which forbids the development of an offensive military force. An American presence in Korea also lets Japan feel secure in a nuclear age without an arsenal of nuclear weapons.

And, despite the recent protests, South Korea seems to understand this. The country of 48 million recently elected a candidate who ran on a platform that emphasized a policy of engaging North Korea regardless of North Korea's reactions or reciprocity. President-elect Roh Moo-Hyun was elected with about 48 percent of the vote. His rival, Lee Hoi Chang, who advocated a firmer policy toward the North seeking reciprocity and a reduction in North Korea's hostile security posture, won 46 percent. Both candidates, and the majority of the citizens of South Korea, continue to recognize the stability and security that the U.S. presence in Korea provides, and they support a continued American presence.

This strong mutual commitment has served both countries well for 50 years. But that doesn't mean this relationship should stay exactly the same. The improvements the U.S. military has made in deploying forces quickly nearly anywhere around the world mean that fewer U.S. forces are required on the Korean Peninsula. This is achievable because the South Korean armed forces' strength, professionalism and desire to shoulder a greater burden for their country's security means that the number and disposition of American troops can be adjusted in consultation with South Korean military leaders. Such adjustments will strengthen relations and cooperation between our two countries.

Make no mistake, though: Keeping U.S. forces in South Korea as long as they are welcome there is good policy. It's important for Americans and South Koreans to remember that for another 50 years, and beyond. The future of peace and democracy in the region depends on it.

Larry M. Wortzel, Ph.D., is vice president for foreign policy and defense studies at The Heritage Foundation, (www.heritage.org), a Washington-based think tank. He is a retired Army colonel who served in the 2nd Infantry Division in Korea, and was a director at the Strategic Studies Institute of the Army War College.