As China increases pressure on Taiwan, the U.S. should increase pressure on Beijing. But the U.S. should not go to war in defense of Taiwan. That's because the U.S. military option for Taiwan is no longer feasible.

China sees Taiwan not as an adversary problem to be resolved by aggressive diplomacy, but as a limb detached from its main body, overdue for surgical reattachment. President Xi Jinping started off the new year warning that he would invade Taiwan if no progress was made toward reunification. Other officials echo this line. In an otherwise detente-style meeting with the chief of U.S. naval operations on Tuesday, top Chinese general Li Zuocheng warned, "If anyone wants to separate Taiwan from China, the Chinese military will safeguard the national unity at all costs ..."

The U.S. should not simply accept China's usurpation of Taiwanese democracy. Instead, Trump should authorize appropriate arms sales to Taiwan, restrain China's absurd harassment of Taiwanese airspace, support Taiwan's accession into international trading arrangements, and increase U.S. diplomatic exchanges. These actions would damage Xi's global interests.

On the flip side, the U.S. military option is just a bad one. To defeat a Chinese invasion of Taiwan, the U.S. would need to strike Chinese military platforms deep inside Chinese mainland territory. The moment the U.S. Navy began intervening to close down Chinese forces around Taiwan, the Chinese military would start firing its long range missiles into the U.S. fleet. In turn, the fleet would either have to stay far away from Taiwan to protect itself, or attempt to destroy the missiles. The problem with the latter option is that it would risk major escalation and fan the flames of Chinese ultra-nationalism.

Would congress authorize the use of U.S. military force in this context? I think not. When it comes to U.S. military options over Taiwan, it's the submarine fleet or nothing. And the submarine fleet isn't enough to alter the balance of outcome.

The best U.S. course of action is not to make war, but to make clear to Xi that he will lose more than he gains by any attack on Taiwan.

Taiwan isn't defenseless. While it spends too little on defense (around 2 percent GDP versus the 4 percent it should spend), it could impose major damage on any Chinese invasion force (assuming, that is, China's immense intelligence infiltration of Taiwan does not gut the Taiwanese military before the fight even begins). Although I'm more skeptical, Tanner Greer offers a case for how Taiwan might effectively resist an invasion.