Beijing on Friday—the 13th no less—threatened the United States with “large-scale war.”

“Prepare for a military clash” said the Global Times in an editorial.

Beijing was hitting back hard against remarks made by Rex Tillerson, Donald Trump’s pick for secretary of State, in his confirmation hearing. “We’re going to have to send China a clear signal that, first, the island-building stops and, second, your access to those islands is also not going to be allowed,” he told the Senate Foreign Relations Committee Wednesday.

The nominee also said China’s militarizing the islands is “akin to Russia’s taking of Crimea.”

Observers gasped at Tillerson’s words, which signaled a radical change in American policy toward China. Yet his general approach toward Beijing, despite all the criticism he has attracted in the last few days, is the correct one for these times.

China has been island building—cementing over coral—all over the South China Sea, but especially in the Spratly and Paracel chains. Beijing began a new phase of reclamation in early 2014 in the Spratlys, in the southern portion of that body of water, creating more than 3,200 acres on and around seven reefs, rocks, and shoals. Admiral Harry Harris, the commander of U.S. forces in the Pacific, famously called the built-up features China’s “great wall of sand.”

Those features, along with Beijing’s nearby possessions, give the Chinese navy and air force the ability to control that body of water.

Chinese leader Xi Jinping, standing next to President Barack Obama in the Rose Garden in September 2015, said there was no intention to militarize the new features.

Despite Xi’s statement, Beijing almost immediately began to fortify the islands. James Fanell, who recently retired as director of Intelligence and Information Operations for the U.S. Pacific fleet, told The Daily Beast he expects a further buildup of military assets on the features, including “forward deployment of both fighter and bomber aircraft to at least one of the three new naval air stations, to be shortly followed by port calls to these deep water harbors by Chinese naval combatants and even submarines.”

The People’s Liberation Army was going to do this anyway, Fanell notes, and the military will probably accelerate fortification, using Tillerson’s testimony and other statements from Trump transition officials as a pretext. Fanell argues Beijing views these words, in and of themselves, as a “threat to China’s sovereignty.”

“Blue national soil” is the term Beijing uses these days. And there is a lot of that. China’s official maps contain nine dashes enclosing about 85 percent of the South China Sea, claiming all the features within the boundary. Moreover, state media, including the official Xinhua News Agency, take the position that the waters inside are also territorial, in other words, internal and sovereign.

The United States and other nations disagree, contending that almost all of the South China Sea is part of the global commons. So did an arbitration panel in The Hague, which on July 12 issued a ruling inconsistent with virtually all of China’s positions.

The decision in Philippines v. China interpreting the United Nations Convention on the Law of the Sea not only invalidated the nine-dash-line claim but also held that China’s land-building activities were violations of its obligations.

Up to now, no nation has been willing to take steps to enforce the ruling beyond mild rhetorical condemnations of Beijing. Tillerson promised the Trump administration will act.

And perhaps not a moment too soon, because China is not only disregarding its treaty obligations, thereby eroding the international system, it is also trying to dismember its neighbors.

The most significant aggressive act in recent years is Beijing’s seizure of Scarborough Shoal. In early 2012, both Chinese and Philippine vessels swarmed the feature, only 124 nautical miles from the main Philippine island of Luzon. Scarborough—just rocks above the waterline—is strategic because it guards the mouths to Manila and Subic Bays.

Washington arranged for both sides to withdraw their craft, but only Manila complied, leaving China in control of the reef.

To avoid confrontation, the Obama administration did nothing to enforce the deal it had just brokered. As Arthur Waldron, the great China historian of the University of Pennsylvania, told me Sunday, “This path of least resistance is very dangerous.”

What the White House did by doing nothing about Scarborough was empower the most belligerent elements in the Chinese political system by showing everybody else in Beijing that aggression in fact worked.

And Waldron is right. The Chinese leadership, emboldened by success at Scarborough, immediately applied pressure on Tokyo to hand over the Senkaku Islands in the East China Sea, continually sending its vessels and aircraft into Japanese territorial waters. Moreover, it appears China soon stepped up efforts to take over Second Thomas Shoal, another South China Sea feature, from the Philippines.

“Xi Jinping cannot quickly back down from Trump’s very public threats” Anders Corr of Corr Analytics told The Daily Beast on Saturday. Although Corr, a leading China watcher, correctly sees Beijing’s war talk after the Tillerson testimony as “public bluster,” many are nonetheless concerned about eventual conflict between the U.S. and China.

And because of that, some think the United States should cede the South China Sea to Beijing. Yet history suggests that would be a mistake. “Whenever peace—conceived as the avoidance of war—has been the primary objective of a power or a group of powers, the international system has been at the mercy of the most ruthless member of the international community,” wrote Henry Kissinger, drawing lessons from Europe at the time of the Congress of Vienna in the second decade of the 19th century. “Whenever the international order has acknowledged that certain principles could not be compromised even for the sake of peace, stability based on an equilibrium of forces was at least conceivable.”

For decades, Washington has tried to manage China’s rise, many times trying to avoid confrontation in the hope that Beijing leaders would one day see fit to “enmesh” their regime in the international system’s rules, treaties, and conventions.

Tillerson on Wednesday essentially said the Trump administration will give up on that effort. Instead of being at Beijing’s mercy, the new team, he signaled, will uphold principles, in China’s peripheral waters and elsewhere.

So on Wednesday you heard the junking of more than four decades of America’s China policy—and the enunciation of a startling new approach that may sound provocative but which is in fact designed to keep the peace.