Chinese President Xi Jinping is moving toward ordering a military suppression of the Hong Kong protest movement.

Doing so would fundamentally undercut the "one-nation two-systems" approach to governing Hong Kong. But it is an increasing possibility nonetheless.

With anti-government protests continuing this weekend (a protest march will go ahead even though it has been banned), Beijing believes its order over the former British colony is fraying. A Chinese ministry of defense spokesman this week warned that the military is "paying close attention to the developments in Hong Kong, especially after riots on Sunday when radical forces besieged the [central government office] in Hong Kong."

The spokesman added that Chinese military forces could be deployed in Hong Kong if the city government requested it.

While Hong Kong officials are hesitant to make such a blatant step, Beijing can decide for them if it so desires. The spokesman's statement cannot be ignored.

Because for Beijing, what's happening in Hong Kong is a major crisis. That understanding is sourced in the ruling Chinese Communist Party's ideological cornerstone: The state's supreme authority must never come into question. This is why, for example, China is also so sensitive about American support for Taiwan. Xi believes any separation from the state is an existential threat to the state. The public nature of the Hong Kong protests, afforded by the greater freedom there than in mainland China, means they pose a special concern to Beijing.

In recent weeks China has increased its Ministry of State Security intelligence presence in Hong Kong. Those MSS officers are helping to identify and monitor protest ringleaders, cajole local crime syndicates (of the kind that attacked anti-Beijing protesters last weekend), and report back to Beijing.

That brings us back to the army issue. Xi doesn't simply need to restore his authority, he needs the widely perceived restoration of that authority. If the protests continue in such visceral form, Xi will put the army onto the streets. Xi knows full well that such action will alienate international businesses in Hong Kong and undercut his keystone "Belt and Road" economic policy. But if Xi believes that the Hong Kong police force cannot do the job, he'll act for them.

Again, Xi regards the supremacy of the state as the first necessity of China's future success. The protests are unlikely to die down. Thus, we should expect to see the People's Liberation Army on Hong Kong streets.