The core parts of the controversial Terminal High Altitude Area Defense ( THAAD ) anti-missile system have been moved to the site of what had been a golf course in southern South Korea. The country's Defense Ministry said South Korea and the US "have been working to secure an early operational capability of the THAAD system." It is believed the system may go into operation next month at the earliest. North Korea marked the anniversary of the founding of its military on Tuesday. The world's attention has been focused on whether Pyongyang would conduct a sixth nuclear test or launch ballistic missiles on or around that day. North Korea has remained quiet in the past two days, but then South Korea took a radical act to begin the THAAD deployment With a bigoted mind-set, conservative forces in South Korea and those advocating nuclear and missile capabilities in North Korea have all lost their rationality.It is infuriating that the US and South Korea have stabbed China in the back at a critical time when China and the US are cooperating to prevent North Korea from carrying out a new nuclear or missile test.But China will not lose its demeanor in the face of South Korea's maliciousness. Sanctioning North Korea is the decision taken by the UN Security Council. China is one of the five permanent members to vote in support. Although the hasty deployment of THAAD disturbs the international sanctions on North Korea, China should not send favorable signals to Pyongyang out of its anger toward Seoul.The issue around the Korean Peninsula is perplexing, while the most urgent task right now is to prevent North Korea from conducting new nuclear tests. As long as North Korea resorts to new tests, China should firmly support the UN Security Council resolutions to impose tougher sanctions against Pyongyang, including restricting oil exports. Beijing's attitude will not change due to the latest moves by Seoul and Washington.As for South Korea, the conservative forces in the country view THAAD not as a deterrence against North Korean missiles, but as a gesture to lean toward the US strategically and as leverage to play hardball with China.South Korea must pay the price for its arrogance. Seoul, by turning the peninsula into a powder keg together with the North, is playing with fire. It undermines China's efforts to ease the tensions on the peninsula, and China will not sit still.With no particular advanced technologies and a tiny market, South Korea had the fortune to become a favorite among major powers and achieved development. However, it does not cherish its position but woos one country to counter another. Its prosperity may just be a flash in the pan.The South Korean military is eager to deploy THAAD, believing it will benefit from it once and for all. But nothing is eternal. With China becoming more powerful and raising its strategic deterrence, it is able to tackle the situation. The trajectory of Northeast Asian geopolitics is not determined by South Korea. Seoul should drop the illusion that it can act at will with Washington as its back.