And it seems Beijing has plans to catch up--fast.

China has a plan: to expand Chinese power globally -- and to overtake the United States.

These are the tenets of a leaked Chinese military document obtained by Japan's Kyodo News.

The internal document, circulated within the Chinese military by the Central Military Commission in February, was intended to convey President Xi Jinping’s desire to strengthen the armed forces.

The document paints a dark worldview, with China confronting “antagonistic blocs of the Western world” that are encouraging separatists in Tibet, Xinjiang and Hong Kong, as well as terrorists and Falun Gong practitioners.

The document calls for the People's Liberation Army, or PLA, to shift its focus from defense of China's coast to land, sea and air operations beyond China's borders.

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“As we open up and expand our national interests beyond borders, we desperately need a comprehensive protection of our own security around the globe,” it said.

It also calls for consolidating the military's command and control system from four tiers to three. By adjusting military strategy, the “balance, dimension and expansion of our strategic goal will be strengthened.” The result will be to "more effectively create a situation, manage a crisis, contain a conflict, win a war, defend the expansion of our country’s strategic interests in an all-round fashion and realize the goals set by the party and Chairman Xi.”

But most interesting is why China is telling its military it needs to reform. The reason, says the Central Military Commission, is that the U.S., Russia, Japan and other nations became strong nations because they had a strong military.

“The lessons of history teach us that strong military might is important for a country to grow from being big to being strong,” according to the document.

“A strong military is the way to avoid the ‘Thucydides Trap’ and escape the obsession that war is unavoidable between an emerging power and a ruling hegemony.”

Military reforms are therefore a significant “turning point” for any given emerging country to “overtake a slower vehicle on a curve,” it said, suggesting that the United States is in its decline.

These are interesting assertions. A challenger with a strong military would seem more likely to push the dominant power into unleashing a preventive war before the challenger gets any stronger -- unless the emerging power is so militarily strong that it can deter a conflict.

Yet at the same time, the document illustrates why China may not overtake the U.S.

"Citing the examples of the collapse of the Soviet Union and political unrest in some East European countries, one chapter said that it is important to control the military in a bid to ensure the Chinese Communist Party’s long-term ruling status," noted the Japan Times.

"History proves that as long as the party keeps a tight grip on the military, it can withstand rigorous challenges both at home and abroad, it said."

The document also stated that one reason the Chinese government weathered the 1989 Tiananmen Square political crisis was the absolute leadership of the Communist Party.

In other words, China's government is so worried about losing its grip on power that it must emphasize that the military is the servant of the Communist Party. Perhaps it's fear that the population can't be controlled without the backing of the military. Perhaps it's fear that the military itself could take over.

America has its problems, one of which is indeed the rise of China and the challenge it presents to U.S. primacy in the Pacific and even on the global level. But for all that, the U.S. government doesn't have to worry that the Pentagon will overthrow its civilian masters.

Michael Peck is a contributing writer for the National Interest.