The Pentagon’s latest National Defense Strategy defines “revisionist” powers as the “central challenge to US prosperity and security,” and China’s recent actions make clear just who tops the list.

Yes, ISIS will attack us at home even after losing territory abroad. And yes, some will insist climate’s our biggest global threat. But, as the strategy paper correctly states, Russia and China, as well as North Korea and Iran, should be our most pressing concerns.

China is rapidly moving to supplant America as the top global power. It’s extending its influence further into South Asia, Africa and South America, to say nothing of its soft-power infiltration activities in the West. But mostly it flexes muscles in its own neighborhood.

On Jan. 4, for example, China unilaterally launched four new airline routes near the median line separating its air space from Taiwan’s, violating a 2015 agreement between the two countries, as well as global treaties. Last week, as part of Beijing’s “island encirclement patrols,” a Chinese aircraft carrier menacingly sailed the Taiwan Straits.

These provocations constitute “a political and military threat to Taiwan, and as such destabilizes the region,” Taiwanese President Tsai Ing-wen said in a statement.

Things are heating up around that little advanced democracy Communist China would love to swallow. And remember: America has long vowed to confront any Chinese annexation attempt — militarily if needed.

Why are things heating up now?

Tsai won the 2016 election convincingly by promising to reverse some conciliatory policies made by her predecessor, Ma Ying-jeou. She’s following through. Taiwanese are increasingly worried about Beijing’s “salami tactic” — an attempt to slowly eat up their country.

They’re watching Hong Kong, where Beijing vowed to maintain democratic institutions and then reneged. And Macaw. And Tibet.

Beijing reacted to Tsai’s election by limiting trade and tourism (Taiwan is a popular destination for China’s well-to-do, and those visits are a major revenue source for Taipei) and by taking other measures meant to inflict pain.

Now it’s further raising the ante, so is a military confrontation next? Will Beijing seek one as pretext for invading and annexing Taiwan?

Taiwan’s military “will bolster its ability to comprehensively monitor and respond to mainland China’s military maneuvering,” Tsai says. But officials in Taipei acknowledge that if Beijing attacks, they can hold on for a few days at best.

Will America rush to the rescue? Our Asian allies are increasingly skeptical, never mind defense treaties and explicit agreements.

They notice that while China’s military budgets grow faster than any in history, ours have been cut over the past decade. And that the United States increasingly talks about retrenchment from foreign military engagements.

President Barack Obama told the Philippines to take its grievances over the fish-rich Scarborough Shoal to an international court in The Hague. Manila did, and won. Beijing then said it didn’t recognize the decision, and now the Scarborough is part of China.

Asian confidence in America is eroding. Time to reverse it.

President Trump’s team is off to a good start. Russian enmity is no longer deemed a Cold War relic. And revamping America’s aircraft-carrier fleet is no longer treated like investing in bayonets.

But talk is cheap, and America similarly talked big about Asia, and about big-power competition, during Obama’s presidency.

Regrowing and replenishing the military will take time, but if America is to remain a global leader, it’s got to start, in earnest, immediately. And a good first step is to recognize China’s top-threat status.

Allies are spooked by North Korea’s nuke program — as are we. But only China’s backing keeps Kim Jong-un’s regime afloat. Without it, he’d likely disappear from our threat list in a New York minute.

Russia and Iran are threats, too. But China is the only power that can seriously challenge America’s economic primacy and, soon, outgrow our military.

Trump must clearly state his opposition to China’s attempts at swallowing its neighbors, like Taiwan. But mostly, he needs to reassure allies, and make clear to competitors, that America’s military is still a top tool in our national-security kit.

And that, if pushed too far, we’re ready to use it.