Illustration: Liu Rui/GT

The US and South Korea said Friday that they agreed to deploy the Terminal High-Altitude Area Defense (THAAD) system as "North Korea's continued development of ballistic missiles and weapons of mass destruction require the alliance to take this prudent, protective measure." The unusual decision on such a highly-watched sensitive issue will alter regional security and Northeast Asia's geopolitical landscape.

Due to the unequivocal opposition of China and Russia, South Korea has been ambiguous about whether to deploy the THAAD system or not. The South Korean public was previously divided over the issue, but President Park Geun-hye, whose five-year term ends in early 2018, made the final decision of deployment, purportedly in response to the North Korean nuclear threat.

The jointly agreed deployment, which came right before the arbitration result on the South China Sea case, may be part of the US portfolio of measures to constrain and irritate China. Whether it is willing or not to aid the US, South Korea may have seized the opportunity to express its veiled dissatisfaction and disappointment with China's way of handling North Korea's nuclear issue.

The deployment decision was not unexpected, but it still set off hot discussions in China.

The Chinese Foreign Ministry expressed strong dissatisfaction with and resolute opposition to the decision and urged the US and South Korea to terminate the deployment. Some people even proposed that China immediately take countermeasures to sanction or punish South Korea.

Anyhow, it is of no use to technically analyze the THAAD system and its possible harm to regional and global strategic balance. The US has realized its phased goal of building a global anti-missile system to have a strategic edge. And in South Korea, public opinion is temporarily dominated by the egoism of conservatism and deceptive slogans of seeking self-reliance.

Strategically the THAAD deployment will prove to be a historically wrong decision. In terms of Northeast Asia's peace and security, Park is opening Pandora's Box.

South Korea's national interests, which combine public opinion, think tanks, political values, factionalism and US pressure, appear more obscure and uncertain than ever before. Security is supposed to be the priority of Seoul.

But shouldn't South Korea feel more insecure than before when nuclear powers like China, the US and Russia jointly object to North Korea's nuclear ambitions and have started sanctioning the latter? Will South Korea obtain more security when its moves jeopardize the strategic interests of China and Russia, which therefore destroys the multilateral mechanisms that check North Korea?

Can it feel more secure by breaking the current nuclear parity and even intensifying the confrontation between US-Japan-South Korea alliance and China, Russia, and North Korea?

The THAAD deployment will help neither denuclearization nor the peace and stability of the Korean Peninsula. On the contrary, it may cause the suspension of international sanctions on North Korea and prompt Pyongyang to take new military adventures. The deterioration of regional security can also give Japan excuses to revise its pacifist constitution and seek to be a military power.

The THAAD deployment will invite a new arms race. It will jeopardize South Korea's relations with China and Russia. Meanwhile, China and Russia will be spurred to enhance the pre-launch viability and penetration capability of nuclear weapons. South Korea stands at the forefront of a possible new Cold War.

In response, China will take actions to protect its national interests and strategic balance, which will affect China-South Korea trade ties. Moreover, the THAAD deployment will lead to further domestic divide and political tumult within South Korea, and debates will be triggered over the location and cost of the THAAD system.

Park's trust-building process on the peninsula in 2013 and "unification bonanza" initiative in 2014 has found little reception in North Korea. Pyongyang conducted its fourth nuclear test in January and declared its nuclear-country status in May, while Park's Saenuri Party lost its parliamentary majority in April.

The frustrations prompt Park to use the THAAD deployment to set South Korea against the North. The fickle mentality over unification and fear for North Korean missiles expose the vulnerability of South Korea's conservative forces.

With the THAAD deployment, the US completes a critical step in its rebalancing strategy to the Asia-Pacific region.

However, a country without military sovereignty can easily become a pawn in great-power contests.

No one believes that Park makes the deployment decision in a hasty manner. But what can a decision that benefits no one bring to South Korea?

The author is director of the Department of International Political Science, College of Political Science and Public Management, Yanbian University. Follow us on Twitter @GTopinionopinion@globaltimes.com.cn