China and North Korea used to be tight. Mao Zedong once said the neighbours were as close as "lips and teeth". But in recent years, China has grown frustrated with the North's potentially destabilising economic woes, as well as a nuclear programme that, from Beijing's perspective, keeps the US military at the gate.
Though critics have long accused Beijing of propping up the Kim regime, the Chinese side responded to last month's rocket test and assassination with what appeared to be a real piece of economic punishment: Beijing suspended coal imports - a financial lifeline for North Korea - until the end of 2017.
Yesterday's test will only deepen Beijing's displeasure. China is the midst of a major campaign against US plans to deploy the anti-missile Terminal High Altitude Aerial Defence (THAAD) system to South Korea. THAAD is a land-based missile defence system that would be operated by US troops station in South Korea. Seoul and Washington argue it is a necessary defence against North Korea.
Today, the White House announced that it will deploy a THAAD battery to South Korea. "The Trump Administration is taking steps to enhance our ability to defend against North Korea's ballistic missiles," White House spokesman Sean Spicer told reporters.
But China hates the plan. To them, THAAD is a security threat designed to undermine the Chinese military, a "strategic plot" hatched by the Americans. In recent, weeks, they've stepped public criticism of the project and also moved to punish South Korea for moving ahead with the plan.
China's party-controlled press is already musing about "destroying" or "blinding" the THAAD system. To express their displeasure with South Korea, China has also denied visas to pop stars and pulled wildly popular South Korean television dramas off the air.
"Let's see how far South Korean TV dramas and stars can go without strong support from the Chinese market," read one editorial in the Global Times, a newspaper known for its nationalist tone.
The US and South Korea are not dealing with the the THAAD issue very well because they have not fully considered China's security concerns
"The THAAD installation is a mighty blow against strategic mutual trust between Beijing and Seoul," the paper continued. "Ties will inevitably hit rock bottom, and this will be a loss for both sides. In the long-run, China needs to get ready to confront Seoul."
"The US and South Korea are not dealing with the the THAAD issue very well because they have not fully considered China's security concerns," said Cui Zhiying, director of the Korean Peninsula Research Centre at Shanghai's Tongji University. "All parties should cooperate on this issue, instead of US and South Korea getting together to suppress China."
And that's just it: China never liked North Korea's missile tests, but right now they are particularly inconvenient. Interrupting China's National People's Congress with yet another missile test makes it harder for Beijing to rail against South Korea's plans because it makes THAAD's stated purpose - shooting down North Korean missiles - seem legit.
China expressed wary dismay at the latest development, with a spokesperson for the Foreign Ministry saying Beijing "opposes" launches that undermine United Nations Security Council resolutions. Behind closed doors, Chinese cadres will no doubt have more to say to their erstwhile friends.