The metrics by which we compare the military strengths of nations often serve as better representation of the countries’ fiscal priorities than their actual combat power. America, for instance, employs the largest, most capable military force on the planet, but because of its diverse obligations and responsibilities the world over, it would be difficult—if not impossible—to amass the entirety of America’s military apparatus in just one region for just one fight.

The fact of the matter is, American hardware and personnel stationed or deployed all around the world often serve as a stabilizing presence and deterrent aimed at nipping future conflicts in the bud before they have a chance to mature into full-fledged threats to America’s security. Such has been the nation’s post-World War II strategy: Stay involved in everybody’s business to ensure a conflict never spills over onto American shores. Even under seemingly anti-interventionist presidents like Barack Obama or arguably isolationist ones like Donald Trump, America’s military might remains distributed far and wide in defense of U.S. and allied interests in places, and even nations, many Americans may never have even heard of.

Therein lies the difficulty in comparing America’s defense apparatus to that of a near-peer competitor like China. China boasts a far larger standing army than the United States, advanced technology initiatives aimed at stealth aircraft and orbital operations, and notably, a Navy that is already every bit as large (or potentially even larger) than America’s. Their tech is largely not as advanced, but the problem is, America’s Navy has dates to keep all around the globe. China’s doesn’t.

In a recent piece by David Axe, published by The National Interest, Axe offers the point that China’s Navy is far larger than most Westerners realize. How large? Somewhere in the neighborhood of 650 sizable vessels. This assessment runs counter to the most recent estimates published by the U.S. Office of Naval Intelligence, but there’s good reason for that: A large portion of those ships don’t actually belong to the People’s Liberation Army-Navy (PLA-N), but rather to one of two other maritime organizations: the Coast Guard or the People’s Armed Forces Maritime Militia (PAFMM).

Now, in the interest of fairness, one could add America’s own fleet of Coast Guard cutters and sea-lift command vessels to its large Navy vessel count, ramping up America’s own figures until they’re comparable to that of the Chinese, but that would offer an even less realistic depiction of forces available to engage in a potential Sino-American conflict. America simply couldn’t deploy all 240 of its large Coast Guard cutters to a fight in the South China Sea. Nor could it devote the entirety of its sea-lift apparatus to such a conflict. In fact, America could not even offer its full 280-or-so-ship Navy to the fight without leaving itself open to significant threats both at home and abroad.

China’s PLA-N lacks the technical or logistical capabilities to serve as a “blue-water” navy, meaning their massive naval force must remain relatively close to friendly Chinese ports for frequent refueling and resupply. This would compromise China’s force-projection capabilities, but in a conflict born out of tensions in the South China Sea, for instance, China wouldn’t need to take the fight to America: The battle and the spoils for the victor would both remain on or below the choppy surface of the contested waterway.

Of course, President Trump campaigned on the promise of a 355-ship Navy, though to date, it remains unclear if the United States will actually achieve that goal any time soon. The number of Navy ships will swell to around 300 in the coming years before beginning to drop again as a number of vessels age out of service. Plans have been discussed to extend the service lives of some vessels, but even that cost-effective solution begs hard questions about how America could sustain a larger navy under projected budget modeling for the decades to come.

“Although the cost of extending the ships’ service life is relatively small compared with the cost of buying all the new ships the Navy wants, the cost of operating and maintaining a 355-ship fleet over 30 years would be much greater than either the cost of purchasing the new ships or the recent budgets for operating today’s fleet,” a Congressional Budget Office report reads. “Recruiting and training those sailors would require more civilian and military positions ashore; additional ships would lead to larger maintenance budgets; and those extra ships and crews would consume more fuel and supplies.”

America may boast the most capable military force on the planet, but in reality, the popular concept of American might being unmatched everywhere it goes doesn’t really stand up to scrutiny. Like the days of the Cold War, a future of American diplomatic and military supremacy is not assured, partly due to the nation’s global approach to both force and influence. Even the greatest military the planet has ever seen can’t be everywhere at once in sizable-enough numbers to bar the swelling of competition from economically viable and militarily focused states like China. It doesn’t take a real peer to compromise American supremacy in a region like the Pacific. Rome didn’t fall to an empire of equal size and capability, it fell because of political instability at home and wide variety of regional opponents throughout the empire and beyond its borders.

America may well find its way to victory over China in another cold to lukewarm competition for diplomatic, economic, and military leverage, but doing so will undoubtedly require some dramatic shifts in approach and strategy coupled with new technologies and rapid procurement. China’s massive presence in their own region, coupled with its aggressive foreign policy and arguably illegal claims of regional sovereignty, does represent a threat to American interests and global stability in the years to come. How America responds will likely dictate who the lone remaining superpower will be in the 22nd century.