Recent press reports that have received little attention in the West indicate that China is quintupling the size of its marine corps, from roughly 20,000 to 100,000 troops.

We really should be paying more attention.

Why does a development like this matter? After all, at least some of the growth will come from moving regular People's Liberation Army units out of the army and under the banner of the marines—moving troops from one administrative basket into another, really. But the fact is, any country needs an army to defend itself, and a large country in a complex region probably needs a large and capable army to pull this off. You only need a large marine corps if you intend to assert yourself overseas.

Just consider the example of the United States. For most of its first century-plus of existence, the U.S. Marine Corps, famously founded in a Philadelphia tavern in 1775, was a highly limited force in both size and capability. With few exceptions, it performed modest tasks in support of the Navy, like port security, limited ship-to-shore expeditions, and putting down the occasional mutiny. This all changed following the Spanish American War, when the United States adopted a much more assertive posture regionally and internationally. Contingents of Marines, already used to operating in relatively small formations and in concert with the Navy, pursued American interests throughout Central America and the Caribbean during the Banana Wars—and in China during the Boxer Rebellion.

At the outset of America's entry into World War One, the Marines' expeditionary experience allowed them rapidly to throw together a brigade to join the allies in Europe. (Hence the slogan, "First to Fight.") In the interwar period, the Corps went all in on the theory that naval infantry were key to securing overseas bases for a global power, and that amphibious landings would be key to such operations. Such planning led to the Marines' leading role in the Pacific in World War Two.

The rise of the U.S. Marine Corps is inseparable from the rise of America as a global power. Put another way, if you have no intention of being a global power, you have no need of a marine corps.

China's marine corps was first established in 1953 and grew rapidly, having been created with a fight for Taiwan in mind. The immediacy of this goal faded for a spell, and the fortunes of the marines faded with it. Re-established in the 1970s, the PLA Marine Corps became a small, specialized force not unlike the early American Marines in some respects—an organization tied to the PLA Navy, with certain commando-like capabilities.

In recent years, in the context of a broader effort to modernize and restructure the Chinese military, the marines' star has risen. A perceptive piece last year in The National Interest surveyed this development, asking if China can "copy the U.S. Marine Corps?" and pointing out how the patterns of major training exercises indicate that the organization was mimicking the flexibility of the U.S. Marines, who have long noted modestly in their hymn that they have fought in "every clime and place." The article asked readers to consider "the potential ramifications of such a Chinese amphibious force maintaining a constant presence in, say, Southeast Asia," or indeed that it "may routinely operate in the Indian Ocean as well—and, for that matter, even in the Mediterranean."

With such an increase in size that we now expect, such expectations are entirely reasonable. Considered along with Beijing's "One Belt, One Road" initiative and its newly aggressive basing strategy, with naval facilities operating and/or under construction in Pakistan and Djibouti, it also seems that merely regional goals are not the extent of China's ambitions. Not that those goals aren't important—indeed, a marine corps that is 100,000 strong, properly supported by airlift and amphibious capabilities (which are also enjoying a surge of investment as part of the PLA's modernization efforts) poses a real threat to Taiwan. Even if a full scale, conventional assault seems reckless and unnecessary, given the other tools that Beijing has at its disposal, the mere credible threat of such an invasion is a powerful political tool in its own right.

Far from a peaceful rise as a nation comfortable with existing international norms and reasonably concerned with its own security, China gives every indication of a desire to call the shots globally. If it achieves such a position, the world will come to miss American predominance—and so will Americans.