If U.S. security is defined in the most narrow way possible--the protection of the U.S. homeland--then indeed China's conventional military capabilities do not yet pose a threat, as Drew Thompson suggests ("Think Again: China's Military," March/April 2010). But successive presidents have defined U.S. security far more broadly, in ways that clash with the purposes of China's military modernization program.

Since the end of World War II, the United States' Asian security strategy has had four key objectives: first, to provide security to East Asian allies, which has allowed them to focus on economic growth and political development; second, to contain any possible regional hegemon that could, like Imperial Japan, dominate the region and even attack the United States; third, to uphold an open and liberal trading regime; and fourth, to maintain the military capability to access the region in order to deter and respond to aggression. The strategy has worked remarkably well. Under the U.S. security umbrella, Asia emerged from colonialism, conflict, and deep poverty to become, for the most part, rich, peaceful, and democratic.

When taking this broader view, China's military buildup is undoubtedly a challenge. China began its military modernization in the early 1990s, when, with the demise of the Soviet Union, its security was improving. One would have to go back to the buildup of the Wermacht in the interwar period or the Soviets at certain points during the Cold War to find a comparable peacetime military buildup. Take China's submarine fleet alone: while the rest of the world's navies, including the United States', have been reducing fleet numbers, China has deployed roughly 38 new submarines in just over a decade. In addition, China's sophisticated integrated air-defense networks, ballistic and cruise missile force, and cyber and space programs are gradually making the seas, space, and air in Asia more difficult for the U.S. military to access.

From this, sensible strategists must take away two key points: one, these military advances are principally the product of China's hegemonic ambitions, and not the result of Beijing facing new and more dangerous threats; and two, the preponderance of advances in Chinese military modernization has an eye toward undermining American military preeminence in the region.

Moreover, the bases that the Chinese arsenal now threaten sit in real countries, where real people live: what may look like a possible, even abstract threat to U.S. military assets is very real to the citizens of Taiwan, Japan, South Korea, and Singapore. What we call "anti-access" challenges are understood by our friends to be military coercion.

Why does this matter? Our allies have counted on our protection and we have counted on their assistance in providing security to the region. Should it look like this bargain is breaking down, our allies will have two choices, neither one good for us. Either they will choose to accommodate China to our disadvantage or they will engage in arms races with destabilizing effects throughout the region.

Right now, it looks to many that we are not up to the Chinese military challenge: our air and naval fleets are shrinking, our bases remain vulnerable, and the use of our carriers looks increasingly problematic. All in all, we have not kept up.

On this point the Asians can speak for themselves: Australia released a defense white paper last year hedging against a hostile China and a diminished United States' presence. India has put forth a "two-front war strategy" explicitly preparing for conflict and naval competition with China. India's plans should be taken as a signal that the it does not expect us to be much help in checking its northern neighbor.

Thus, China's military threat has already forced our allies to reconsider their security strategies. We still have time to reassure them that the grand bargain remains in place--we provide security with their help, while we all continue to prosper in an open and free trading system. The bargain has paid great dividends for all. But China's military threatens to break it.

Dan Blumenthal is a resident fellow at AEI.

Photo Credit: iStockphoto/graham heywood