Seoul's decision to deploy the THAAD system has harmed Chinese-South Korean relations significantly, prompting multiple warnings and countermeasures from Beijing. Compared with voices in the government, the Chinese public has expressed drastic opinions, calling for the punishment of South Korea.

Among the proposed punishments, one suggests that China reconsider its ties with North Korea, adjust its Korean Peninsula policies and provide military aid to North Korean if necessary.

But whatever it ends up doing, Beijing should never consider developing closer ties with Pyongyang so as to once again become North Korea's protector. In particular, Beijing cannot back down on its stance against the North Korea's nuclear ambitions.

In so doing, China would not only cause South Korea to side entirely with the United States, but also would find itself allied with North Korea, a situation that would amount to a new Cold War. In the long run, the standoff would be extremely detrimental to China's development and strategic security.

Seoul's agreement to deploy THAAD didn't come abruptly. Park Geun-hye had long considered it, and the final decision must have been the result of the pressure from the United States. At the same time, Beijing's failure to contain North Korea's nuclear program may be another important reason.

Beijing believes that it spared no effort in solving the North Korean nuclear issue, but South Korea, along with some Western countries, thinks otherwise. In Seoul's opinion, Beijing has the power to force changes in North Korea but has been unwilling to make it happen; Seoul therefore thinks that Beijing has been assisting Pyongyang, or has at least been unwilling to impose sanctions.

But Beijing has its own difficulties, too. For Beijing, which is poised to punish South Korea, there are more important questions to think over: What is China's fundamental interest on the Korean Peninsula? How could it maximize this interest? In the competition between the two Koreas, which side will eventually prevail? If China cannot find answers to these questions, China's North Korea policies and Korean Peninsula strategies will go astray.

Any reasonable person can tell South Korea will be the one that prevails in the end. If the Beijing-Seoul ties deteriorate, the latter will consider Beijing as a stumbling block for the reunification on the Korean Peninsula. The new country built after reunification will be hostile to China.

Given the balance of power between China and South Korea, Beijing could well ignore this potential hostility. But one has to note that the reunified peninsula doesn't simply mean an expanded South Korea, but a stronger nation backed by the United States and Japan. Even though China could win if a contention starts, such a struggle would consume much national power, thus affecting China's rise.

Therefore, China's fundamental interest in the Korean Peninsula is to prevent a hostile government once the two Koreas reunify. To ensure that, China mustn't develop close ties with North Korea.

For its own fundamental interests, Beijing shouldn't adjust its Korean Peninsula strategies, let alone provide military aid to North Korea. Despite Seoul's decision for THAAD deployment, it doesn't necessarily mean Seoul has completely turned to Washington. But if China reembraces North Korea, then Seoul will readily become a U.S. protégé.

  Deng Yuwen is a fellow with the Charhar Institute.  

  The article was translated by Chen Boyuan. Its   original version     was published in Chinese.