Has the United States crossed a Chinese “red line” with this military presence? You might have thought so. Last year, an annual Pentagon report on China listed “foreign forces stationed on Taiwan” as one of seven issues on which China had said it might use military force against the island. But Newsweek noted that in this year’s version of the report, released Wednesday, the “foreign forces” pretext was dropped.

Military planners can’t afford ambiguity. So China’s war plans for Taiwan assume that the U.S. military will become involved, according to a leading China analyst who requested anonymity. He said China’s goal is to seize Taiwan in five days, before the United States is able to land forces.

America won’t deter such an attack with the aircraft carriers we once sailed boldly into the Taiwan Strait. Today, those behemoths are prey to Chinese precision-guided missiles. Instead, the counterweights against China are three largely invisible factors: America’s alliances with powerful Pacific neighbors such as Japan and Australia; its unmatched dominance of undersea warfare; and its ability to help Taiwan fight an asymmetric war that would be very costly for China.