In the event of a Communist Chinese attack, the toll in defending Taiwan would be so great that it “would break the back of U.S. military power for a generation.” That is the conclusion of an architect of a new war game conducted by the Center for Strategic and International Studies, Matthew Cancian.

That does not mean defending Taiwan and holding the line against Chinese aggression is not worth the cost. Plus, Mr. Cancian adds, Communist China’s military would also be destroyed. So, he says, “it’s not like we lost our military and now somebody else is gonna be taking over the world.” Yet, unlike China, America has global commitments and risks that require a military presence, including new ones that might arise in the wake of a battle over Taiwan.

The new war game offers a breathtaking glimpse of the scale of the fight. The war game team estimates that in the first three weeks of conflict America would lose between 200 and 372 aircraft; between eight and 18 large warships, totaling between 9 percent and 18 percent of our force; and between two and 11 American aircraft carriers, with between 4,000 and 10,000 service members killed in action. Some 50,000 Americans were killed in the entire Vietnam war.

The losses are framed in generational terms because it would take decades to replace some of the destroyed equipment. While aircraft would only take an estimated four to five years to rebuild, according to Mr. Cancian’s father, Mark Cancian, the leader of the CSIS war game, it would take decades to replace the ships, and, given shipbuilding limitations, between 20 years and 30 years to replace the aircraft carriers. 

It is difficult to overstate “how much of a shock this would be to the United States,” an MIT researcher and participant in the war game, Eric Heginbotham, says. “We have not fought a war like this since 1945 and the scale of the losses would be beyond anything we’ve experienced for generations. The military has been quite accustomed to operating in sanctuary, particularly the Air Force and the Navy.”

To reduce the cost of defending Taiwan, the team recommends a few key steps. The first is to buy more anti-ship missiles, specifically long-range air-launched missiles. They are weapons designed to sink Chinese ships, which would be easy targets as they approach Taiwan and sit offshore.

Mr. Heginbotham points out that these missiles have great versatility. “You can launch them from submarines,” he says, “you can launch them from surface ships, you can launch them from tactical aircraft, and you can launch them from bombers.”

Unfortunately, our inventory of anti-ship missiles, Mark Cancian says, is  limited. The war game shows American forces running out of them in the first week of the battle for Taiwan, after which the Yanks would have to start shooting shorter-range missiles, which would likely lead to major aircraft losses. 

The war game team also recommends the American military shift away from surface ships, which Matthew Cancian says do not appear to be “survivable within a significant distance from an enemy’s coast.” Instead, it recommends we invest in bombers and submarines that can get in, shoot long-range anti-ship missiles, and get out without being destroyed. 

The bomber, Mr. Heginbotham says, is “the most important U.S. piece on the board. The bombers can fly from Alaska or Hawaii or wherever you want them to fly from and deliver 20 of these big missiles at a time … and then fly back.” This is because Chinese air defenses cannot meet the missile range of 375 miles.

The second recommendation, Mr. Heginbotham says, is to “pour a ton of concrete … to build hardened air shelters up and down the length of Japan” and elsewhere so as to protect land-based aircraft. Hardened shelters aren’t 100 percent effective, but they would require the Chinese to use many more missiles and, as a result, our losses would go down. We also need to harden ports and ammunition depots, he adds. 

“The Chinese,” he says, “have a lot more air fields closer to Taiwan than we do … and they’ve got a very large inventory of accurate ballistic and cruise missiles.” This means that “everything is vulnerable,” he says, and the Chinese “can cover most of those air bases, for some period of time at the outset until they run out of missiles.”

The third recommendation is to accelerate arm sales to Taiwan, with a focus on survivable weapons, such as mobile anti-ship missiles and mobile anti-aircraft missiles instead of the fighter jets and large ships that Taiwan has traditionally fielded, which would be highly vulnerable. 

These systems may have made sense in the past, Mark Cancian says, but they don’t anymore given Communist China’s military modernization. Mr. Heginbotham says the Taiwanese are “spending money on a lot of the wrong things. They should stop buying big warships and stop spending a lot of money on combat aircraft. They just need a credible army, and it would be good if they had survivable mobile anti-ship missiles.”

Would Mr. Heginbotham recommend “loading the Taiwanese up with anti-ship missiles”? Not necessarily. “There are Chinese spies all over Taiwan,” he says, “and if they happen to hit the depots the first day, and you’re really depending on that to survive, then you’d be out of luck. Anything we put into Taiwan can just get slaughtered.”

“Going forward in procurement for Taiwan,” Mr. Heginbotham continues, “I would absolutely trade ships for missiles. I’m not sure I would trade the army for anti-ship missiles though, because that’s the one piece that we cannot substitute out with American power. The U.S. power can do everything else but the Taiwanese have to fight that ground battle and ensure that we have the time to bring our capabilities to bear.”