How China could stop a US strike on North Korea — without starting World War III

After North Korea tested a salvo of ballistic missiles designed to defeat US and allied missile defenses in the Pacific, speculation has risen about a possible US "decapitation strike" on North Korea. 

With the help of Stratfor's Sim Tack, Business Insider detailed how such a strike would likely play out, but in the interest of keeping the article focused, we omitted a major player — China.

Here's how China would respond if the US were to attack the hermit kingdom.

SEE ALSO: US rejects China's plan to get North Korea to stop developing nukes

China has interests in preserving the North Korean state, but not enough to start World War III over.

China may not endorse North Korea's nuclear threats toward the US, South Korea, and Japan, or its abysmal human-rights practices, but Beijing does have a vested interest in preventing reunification on the Korean peninsula.

Still, China's proximity to North Korea means that the US would likely alert Chinese forces of an attack — whether they gave 30 minutes' or 30 days' notice, the Chinese response would likely be to preclude — not thwart — such an attack.

China sees a united Korea as a threat.

"A united Korea is potentially very powerful, country right on China's border," with a functioning democracy, booming tech sector, and a Western bent, which represents "a problem they’d rather not deal with," according to Tack.

The US has more than 25,000 troops permanently stationed in South Korea, but no US asset has crossed the 38th parallel in decades. China would like to keep it that way.

And without North Korea, China would find itself exposed.

For China, the North Korean state acts as a "physical buffer against US allies and forces," said Tack. If the US could base forces in North Korea, they'd be right on China's border, and thereby better situated to contain China as it continues to rise as a world power.

Tack said that China would "definitely react to and try to prevent" US action that could lead to a reunified Korea, but the idea that Chinese ground forces would flood into North Korea and fight against the West is "not particularly likely at all."