China threatened the U.S. on Tuesday over a newly approved $2.2 billion American arms sale to Taiwan.

Via its Global Times propaganda outlet, China posited that "The U.S. and Taiwan must not step out of line; otherwise, a price must be paid." The article continued, "We might as well make a bold assumption. If an arms sale between the U.S. and Taiwan is not acceptable to the Chinese mainland, if the latter announces it would resolutely destroy the equipment once they are placed on the island, what would happen?"

Interestingly, the Chinese government also used its article to claim that the U.S. sale has no threat-potential. And that invites the question of why, if China believe this sale doesn't significantly strengthen Taiwan's defenses against prospective invasion, is Beijing also so aggravated? First, because it's a lie. China knows this sale does indeed effectively improve Taiwan's defense portfolio. Battle tanks, armored vehicles, and man-portable Stinger anti-aircraft missiles, were specifically chosen to contest Chinese military gaps in the early stages of any invasion. It's a common misconception that naval invasions are now simple because we're in the 21st century or something. China knows that crossing the more than 80-mile Taiwan Strait will likely entail taking major casualties from Taiwanese missile, artillery, naval, and air forces (especially if U.S. Navy submarines come into play).

In turn, Chinese planners expect that the earliest landing forces that do reach Taiwanese soil will have to fight without effective air-ground support. This is where Taiwan knows it can win: by using highly mobile forces to isolate and annihilate pockets of landing troops. While China would use its mainland missile forces to wreak havoc on fixed Taiwanese positions such as air bases and depots, it would struggle to target mobile Taiwanese forces. That's where these new tanks and stingers come in. And if the Chinese advance force can't get off the beaches, well, China has a big problem.

Another issue is politics. China is infuriated that President Trump is not blinking. At the recent G-20 summit in Japan, Trump acquiesced to Xi's demand that he allow U.S. companies to sell goods to China's Huawei telecommunications firm/intelligence service. Xi thus had reason to believe that Trump was buckling in desperation to get a trade deal before the 2020 election. This arms sale tells a different story.

The U.S. remains committed to restraining Beijing's aggressive expansionism. Prudent about Chinese sensitivities over Taiwan, we should still support our democratic island ally and refused to be cowed by Beijing's threats.