The U.S. and South Korea conducted joint military exercises in East China Sea from July 25 to 28 – the largest exercise since 1976.

Of course, this show of force is a direct result of the sinking of the South Korean warship, Cheonan, on March 26. The U.S. condemned North Korea and threw full support to South Korea after a South Korean-led investigation named the North responsible. The U.S. also declared that it would hold a joint anti-submarine military exercise in the East China Sea. Its intent is quite clear, warning the North Korea not to take reckless action.

This seems to indicate the U.S. has changed its policy toward North Korea and will now pursue containment. Obama is not confident in denuclearizing the Korean peninsula without a political power shift in North Korea, and he seems to have lost interest in the Six Party Talks, though it's not been publically stated.

The Obama administration maintains that it's been strategically patient with the North. However, I believe the U.S. didn't seriously prepare for resumption of the Six Party Talks. It has changed its policies to promote UN sanctions to bolster its containment of the North Korea.

The future stability of the North is in question, as Kim Jong Il's health has reportedly worsened and currency reform has failed. It's logical to conclude that the Obama administration thought the possibility of turbulence during the power transfer could be used to contain North Korea and make the country collapse, so the Cheonan incident was viewed as a big opportunity for the U.S.

For South Korea, the exercise is significant. Because the UN Security Council didn't directly condemn the North, South Korea suffered a diplomatic loss. It hoped the U.S. could help in a process of revenge. But with the US economy in recession and managing two ongoing wars, the U.S. lacks the energy to get entangled with North Korea.

The U.S. would have liked to downplay the incident, but it felt it had to strongly back an ally. Subsequently, the military exercise became the best and only way to warn and deter the North while also satisfying South Korea.

When the news of the joint exercise came out, China reacted unusually fierce. Ma Xiaotian, deputy chief of the army's general staff, said China strongly opposed the exercise. In just two weeks, China's military and foreign ministry stated its opposition five times.

Many observers said the U.S. is actually targeting China this time. But this is not convincing. No doubt, due to historical reasons, China is an inevitable target of the U.S. and South Korea, but this exercise is more about targeting the DPRK.

The Cheonan sank into the Yellow Sea, so it's reasonable for the anti-submarine drill to take place there. Last year, the USS George Washington joined in an exercise in the Yellow Sea, and China didn't oppose it, and it was a low-profile exercise, so many weren't even aware of it. Although the geographic location of the Yellow Sea directly concerns China's immediate interests, the U.S. and Korea operate in international waters. However, in the shadow of Sino-U.S. setbacks this year, many Chinese view the U.S. negatively.

This exercise will increase China's strategic suspicions against the U.S. The high-level military exchanges between China and the U.S. have already halted. This exercise just outside the China's border will no doubt add fuel to the fire regarding the Sino-U.S. relations. Kenneth Lieberthal, a renowned American expert on China, recently said to Lianhe Zaobao that despite the strategic partnership, China and the United States still harbor deep suspicions about each other, which is the biggest failure in the nearly 30 years of Sino-US diplomacy. The dispute over the reaction to the Cheoan sinking is the latest evidence.

The unresolved Cheonan incident that led to this military exercise doesn't deserve fierce opposition from China. Instead, China should agree to resume Sino-US military exchanges and express the security concerns about weapon sales to Taiwan instead of remaining standoffish. This year marks the 60th anniversary of the Korea War. While remembering the martyrs, Chinese people should also learn some lessons from this war and avoid repeating the same mistake.

The author is a research associate with China Institutes of International Studies.