"To join a U.S.-Japanese anti-Chinese coalition would not only antagonize China, it would align Korea with its "ancient foe." Worse, the mutual U.S. alliances mean that nationalists and maximalists in Korea and Japan can make whatever outrageous claims they like about the other, yet face little geopolitical consequence. U.S. alliances are a form of "moral hazard" that ironically worsen the problem by reducing the incentives for rapprochement."
The recent trip by U.S. Defense Secretary Chuck Hagel to Japan, with its strong affirmation of the U.S.-Japan alliance, has sparked a major, arguably grand, strategy debate in the Korean media. In the almost six years I have taught international relations in Korea, this is the most far-reaching debate I have yet seen. Koreans are increasingly aware that they are stuck between the U.S. and China, that Japan is increasingly openly aligning against China, and that the U.S. pivot to Asia is not a broad-based "cultural reorientation" of the U.S. as a "Pacific country," but a straightforward military-diplomatic "let's-not-call-it-containment" effort to prevent China from dominating Asia. (Variations and expansions of the following argument may be found in my recent essays at Newsweek Korea and Newsweek Japan.)
Non-Koreans, particularly Americans, tend to assume that Korea will simply line up with the United States, Japan, Australia, and other regional democracies. The American conversation about Asia, not surprisingly, is dominated by China. China has 1.3 billion people. It is the world's second largest economy. Its rise is ending the period of U.S. sole superpowerdom, what international relations theory calls "unipolarity," creating great angst that the U.S. is in decline. Worse, it is an authoritarian great power, frequently compared to Wilhelmine Germany. There is a broad fear that China is seeking to forge something like a Sinic "Monroe Doctrine" and push the U.S. in the Pacific back to Hawaii. Hagel's visit to Japan made all this pretty clear, as he tacitly endorsed Prime Minister Shinzo Abe's Japanese nationalism and an expanded JSDF (Japanese Self-Defense Forces) role.