The level of fury expressed by Beijing over South Korea's recently announced decision to deploy the U.S. Army's Terminal High Altitude Area Defense System (THAAD) seems to have caught some in Seoul off guard. China's official mouthpiece, Xinhua, even carried an August 13 report suggesting that President Park could be "impeached" over the THAAD decision: "A South Korean opposition party candidate said it is possible to impeach President Park Geun-hye over her turning a blind eye to growing public opposition over the deployment of the Terminal High Altitude Area Defense (THAAD) on the country's soil."

President Park, however, forcefully defended her decision on THAAD deployment in her annual August 15 Independence Day speech, laying the blame for its necessity squarely at the feet of Pyongyang. Park said that the planned deployment at the end of 2017 of the advanced U.S. missile system is a "self-defense" measure necessitated by Pyongyang's "senseless" provocations. She called on North Korea to "immediately" cease its nuclear program, stating that its saber-rattling would only aggravate its isolation and economic travails.

Beijing has taken a decidedly different view, however, seeing THAAD as not just a response to North Korean missile launches but as a not very veiled means to contain a Chinese military build-up. And if looks could kill, South Korean foreign minister Yun Byung-se would be gone. The scowl displayed on the face of Chinese foreign minister Wang Yi, when he held a bilateral meeting with his South Korean counterpart at the recent ASEAN Regional Forum in Vientiane, Laos, said it all. Foreign Minister Wang said that "the recent behavior from South Korea has undermined the foundation for our bilateral trust," by "pushing to deploy an advanced missile system on the Korean Peninsula" despite Beijing's strong opposition. Wang reportedly delivered an even more severe tongue-lashing to Yun behind closed doors.

Beijing also used its diplomatic muscle on August 11 to block a UN statement condemning recent North Korean missile tests, which included a medium-range ballistic missile that landed within the waters of Japan's exclusive economic zone. The Security Council non-action against the latest North Korean provocation will likely serve to weaken the whole UN sanctions regime imposed on Pyongyang for its continued nuclear and missile testing.

Seoul and Beijing's relations had blossomed over the past few years based upon a shared concern over history issues regarding Japan and a strong personal rapport between the South Korean and Chinese presidents. The emergence of a new strongman in Beijing, Xi Jinping, the son of a founding revolutionary of the People's Republic, at the same time that an aristocratic Sinophile, Park Geun-hye, was elected in South Korea as president, following in her late father's footsteps, laid the groundwork for what appeared to be a political marriage made in heaven.

These two "princelings" shared a warm personal rapport as they exchanged official visits between Beijing and Seoul even as North Korean bad boy Kim Jong-un was left out in the cold. Park even went so far last summer as to nettle some in Washington by being the only major ally to attend Xi Jinping's anti-Japanese-parade-disguised- as-a-WWII-victory-parade in Beijing.

But those heady days are over now. The mutual misreading is now leading to bitter acrimony and a precipitous cooling of relations. Seoul, since the establishment of diplomatic ties with China in the early 1990s, has sought to juggle rapidly expanding Chinese commercial ties against its traditional security ties with its American ally. Yet it seems to have seriously underestimated the wrath of China.

Beijing, on the other hand, seems to have miscalculated that, in giving Seoul deliverables on history issues such as a memorial to Korean independence fighter An Jung-geun and a new Comfort Women museum in Nanjing, it could now exercise a veto power over Seoul's defense decisions with its U.S. ally. But while Xi could deliver on history, he failed to provide President Park with what she wanted as far as curbing North Korea's continued erratic behavior. So Park swung back toward her allies, giving the green light to Washington for the long-sought THAAD deployment and entering into a rather domestically risky deal with Japanese Prime Minister Abe on the long-smoldering Comfort Women issue.

Park has further allowed the THAAD feud to enter into domestic South Korean politics by raising questions about the patriotism of some opposition National Assembly Members. A group of them recently traveled to Beijing to discuss the fallout over THAAD.

Members of Park's governing party rather pointedly referred to those traveling to Beijing– a destination once favored by the South Korean president herself – as "traitors" and "flunkies of China." However, the opposition Minjoo Party is looking toward next year's South Korean presidential election campaign, where it perceives THAAD as a potential stick with which to hit the ruling party for disrupting commercial relations with China. Some in the "progressive" opposition may also possibly wish to stir the latent anti-American feelings in a significant number of South Koreans.

Seoul has made the distinct calculation that commercial relations with China, its largest international trading partner, will not be hurt by the THAAD missile defense system deployment. However, further fallout over the THAAD has already included Beijing playing the entertainment card: Aju, a news service, reports that "China canceled a series of fan meetings planned by South Korean celebrities last week after a top media regulator warned of a setback in exports of South Korea's pop culture wave 'Hallyu' to China."

And it could become even more severe. Bloomberg reported on August 12 that "China is considering steps such as limiting imports of South Korean goods and services as it seeks to apply pressure on Seoul not to deploy a U.S. missile shield system, according to people familiar with the matter. Authorities are also considering the suspension of some investments and acquisitions in South Korea, said the people, who asked not to be identified because the discussions are private. China is also assessing the impact of steps already taken on visas and in the entertainment and tourism sectors, they said." Beijing has been known to use commerce as a club in foreign policy disputes in the past, such as when it waged a "banana war" with the Philippines over the South China Sea.

The South Korean political establishment clearly underestimated the severity of Beijing's pushback. And Beijing's ultimate political payback could be yet to come— extending that long-anticipated invitation Kim Jong-un to visit China. That would be a THAAD story indeed.

Dennis P. Halpin, a former adviser on Asian issues to the House Foreign Affairs Committee, is a visiting scholar at the U.S.-Korea Institute (SAIS) and an adviser to the Poblete Analysis Group.