If he did, Xi would pocket the American concession until next time. The new normal would constitute the baseline for the next round of summitry. At that point Xi would try to coax Trump into negotiating away some other part of freedom of the sea. Over time, if successful, China would persuade America to surrender freedom of the sea by increments. It would be reduced to freedom of navigation, a minor subset thereof—and Beijing’s salami-slicing approach—would have paid off handsomely at the bargaining table.

Maritime freedom is indivisible, and should be sacrosanct. Trump should refuse to barter away the liberal maritime order over which the United States presides. Before he can do that, he must recognize that’s what he’s being asked to do.

Allies Are Watching

A hard fact must remain uppermost in mind, namely this: America has no strategic position in Asia without allies, and allies will afford this week’s proceedings close scrutiny. If Tokyo, Seoul, or Manila loses confidence in the Trump administration’s determination to keep U.S. treaty commitments in Asia, they could reduce U.S. access to harbors and bases on their territory—or, in the worst case, refuse access altogether.

That would spell trouble for U.S. maritime strategy. Sea-power theorist Alfred Thayer Mahan observes that ships bereft of overseas naval stations are like “land birds,” unable to fly far from home shores. So it was when Mahan was writing a century ago; so it remains today. U.S. naval and air forces can accomplish little when operating from Guam or Hawaii, hundreds or thousands of miles from potential battlegrounds. Still less can they execute missions in Asia from North America.

For the first time since 1898, the United States could find itself without the ability to mold affairs in Asia. Reassuring host nations is not merely something that’s nice to do. It is imperative unless America wants to retreat to the Western Hemisphere. How to reassure them? About sixty years ago Henry Kissinger devised a simple formula to estimate one combatant’s ability to deter another. His formula also helps us estimate one ally’s ability to reassure others that it will keep faith with them.

To riff on Kissinger’s ideas, reassurance is a product of capability, resolve and belief. Suppose U.S. leaders want to reassure Japan that they will direct U.S. forces to help defend the Senkaku Islands. In that case they must field military capabilities adequate to that mission, demonstrate the gumption to deploy those capabilities when the time comes, and make the Japanese leadership and citizenry believers in American capability and resolve.

Kissinger stresses that his equation involves multiplication, not addition. If any of the three factors drops to zero, consequently, so does Washington’s capacity to reassure allies and friends. (And so, by the way, does its capacity to dismay and deter prospective foes like China.) Overpowering armed might means little absent the willpower to use it. Neither capability nor resolve avails if the ally—rightly or wrongly—doubts the U.S. leadership will uphold its treaty commitments.

President Trump and his advisers must maximize all three factors lest Asian governments lose confidence in America—and make the best deals they can with Beijing, in hopes of muting Chinese displeasure with them in a post-American Asia. Allies, then, constitute a crucial audience of this week’s summitry. They will parse every word out of Mar-a-Lago.

And so will China. Sun Tzu advises sovereigns and generals to attack their enemies’ strategies and alliances first to bolster prospects for strategic success. Sun’s “Hegemonic King” is a consummate alliance preventer and wrecker. He’s big and brawny. He overawes weaker neighbors, keeping them from making common cause against him. And he vastly outmatches any neighbor in a one-on-one contest—conferring crucial negotiating leverage.

President Xi, contemporary China’s Hegemonic King, will likewise be on the lookout for opportunities to loosen the bonds between the United States and its Asian partners. This is a real prospect. President Trump’s focus on burden sharing within U.S. alliances is laudable, but remember: Asia is different than Europe. It’s one thing to expect NATO allies to assume a greater share of the load. After all, Germany is deeply embedded in European institutions. There is approximately zero chance that Germany will rearm and go on the march once again, and Europeans know it.

Europeans, consequently, can invest more in their common defense without the anxieties about the titan in their midst that afflict Asians. Japan is different. There was no counterpart to NATO or the European Union within which Japan could safely rearm in the postwar years. There’s still no such counterpart. The lopsided arrangement that is the U.S.-Japan alliance—of which Japan’s exceedingly frugal defense budgets are part—is a product of decades of U.S. policy, not Japanese freeriding on American taxpayers.

America spent on Japan’s defense so Japan didn’t have to—and so fellow Asians could rest easy. Bottom line, the strategic settings in Western Europe and East Asia are different. It’s one thing to demand more from Europe, quite another to demand that Japan shuck off decades of painful history overnight. Implying that the United States might abandon Japan would be unfair to an ally that has been unfailingly deferential to U.S. wishes. Speedy rearmament, furthermore, would be politically infeasible for any leadership in Tokyo.

Defense Secretary Jim Mattis delivered a message of reassurance during his February tour of Asia. That’s a message Washington ought to broadcast early and often. Let’s hearten friends this week. Only then should we placate prospective antagonists.

James Holmes is professor of strategy at the Naval War College and coauthor of Red Star over the Pacific. The views voiced here are his alone.

Image: Xi Jinping at 2016’s U.S.-China Strategic Dialogue in Beijing. Flickr/U.S. Department of State