Last Monday, Qin Gang of the Chinese Foreign Ministry announced that China Coast Guard vessels on the previous day had prevented two Philippine-flagged ships from approaching Second Thomas Shoal. Beijing’s sailors “spoke through amplifier” and warded off the intruders, the spokesman explained. “It is known to all that China has sovereignty over the Nansha Islands and their surrounding waters, including the Ren’ai Reef,” said Qin, using Beijing’s name for the shoal.

In fact, only Beijing thinks China has sovereignty over Ren’ai, which Manila calls Ayungin Shoal. The long and thin coral outcropping is part of the Spratlys, 250 islands and reefs covering 165,000 square miles of the South China Sea. The contested reef is 105 nautical miles from Palawan Island of the Philippines. Hainan Island, China’s closest point, is about five times farther away.

Beijing has expansive territorial claims in the area. Its official maps contain nine dashes, in the form of a tongue, that encompass about 90 percent of the South China Sea, recognized by all states other than China as international water. Beijing’s apparent claim is inconsistent with obligations it has undertaken by treaty and has no support in international law.

In recent years the Chinese have employed rough tactics to enforce their designs on the area. In early 2012, for instance, China’s vessels first surrounded and then took control of Scarborough Shoal, a part of the Philippines about 120 nautical miles off the main island of Luzon. In June of that year, both Beijing and Manila agreed, after mediation by Washington, to withdraw their craft from Scarborough’s waters. Only Manila did so, however, and to this day Chinese ships prevent Filipinos from returning to their traditional fishing grounds.

Chinese state media brazenly boasted of their government’s seizure, and Chinese military officers, emboldened by success, now arrogantly trumpet their provocative acts. Major General Zhang Zhaozhong, for instance, described what he called the “cabbage strategy” that was successfully employed to seize Scarborough. By wrapping an island “layer by layer like a cabbage” with small vessels, Chinese forces could keep out the ships of other nations.

At Second Thomas Shoal, China is using a small flotilla to strangle a tiny Philippine garrison. There, Manila in 1999 grounded the Sierra Madre, a World War II-vintage hospital ship, to mark its territory, leaving a handful of marines on board. As General Zhang explained, China, with its cabbage tactics can block resupply of troops like those on that rusting vessel. Without provisions, the troopers stationed there will be forced to leave after one or two weeks. “Once they have left, they will never be able to come back,” Zhang gloats.

That’s obviously why the Chinese craft turned back Manila’s two vessels last Sunday. And Beijing’s action was an escalation of the situation. “For 15 years we have conducted regular resupply missions and personnel rotation without interference from China,” said Philippine Department of Foreign Affairs spokesman Raul Hernandez at the beginning of the week. Beijing’s vessels did not block a supply run in June 2013.

Why did the Chinese decide to act at this moment? Ernest Bower of the Washington-based Center for Strategic and International Studies told Reuters that their belligerent move could be the result of their perception that Washington was less than resolute in Syria and Ukraine so it would be similarly weak in the South China Sea. That’s an interesting theory, but there is a more direct explanation. The Chinese know that the U.S. did nothing to challenge them after their clear act of aggression in taking Scarborough. To make matters worse, Washington did not react even though they had repudiated the agreement it had brokered.

The U.S., over the course of this and the preceding two administrations, has tried to defuse tensions in the South China Sea and ensure that completing claims—seven nations assert sovereignty to reefs, shoals, and islands there—are settled peacefully. To that end, Washington, the ultimate guarantor of security in the region, has walked many fine lines. It has, for instance, tried to “engage” the Chinese, maintaining good relations with them but also cajoling and constraining them from time to time. America has also reassured allies and friends but has, at the same time, been concerned about emboldening its partners with too much backing. Ely Ratner, who served on the State Department’s China Desk, borrows an apt sailing metaphor and likens this inconsistent-looking process to “tacking.”

In generally peaceful times, tacking has worked, but now it is not. It has obviously not restrained the militant Chinese—or not restrained them enough—and it has dismayed others, with the result that countries on China’s periphery look set to take action on their own, which will complicate the regional situation for Washington.

The problem for America is that Beijing has set out to commit aggression in small increments, such as Major General Zhang’s “cabbage” tactics, so as to not invite retaliation. The Japanese call China’s acts against their territory, which resemble Chinese provocations directed against the Philippines, “grey zone” incidents.

U.S. and Japanese defense officials are now looking at grey events as this year they update bilateral defense guidelines that have not been revised since 1997. During early discussions, Washington’s representatives have been tacking, giving Tokyo the impression that America is afraid of antagonizing Beijing. Reuters reports that a “U.S. defense official” denies this is the case and believes the two long-time allies need to produce general guidelines that are “flexible and responsive.” Focusing on China, according to the American official, is “too simplistic a narrative.”

Tokyo’s view may be simplistic, but only one nation threatens Japan. The Chinese are pressuring Japan and see American reluctance to confront their belligerence as evidence that they are successfully intimidating the U.S.

China’s assessment is commonly shared in the region. While Washington sees its actions as restrained and responsible, others perceive them to be inadequate and feckless. Last month, Philippine president Benigno Aquino voiced the view out loud, declaring that his country was not going to accept its piecemeal dismemberment by China. “If we say yes to something we believe is wrong now, what guarantee is there that the wrong will not be further exacerbated down the line?” he asked in a New York Times interview. “At what point do you say, ‘Enough is enough’? Well, the world has to say it—remember that the Sudetenland was given in an attempt to appease Hitler to prevent World War II.”

The People’s Republic is not the Third Reich, but Aquino’s comparison between 1938 and now should make American policymakers uncomfortable. Washington, after all, did not confront the Chinese over Scarborough, letting them take control of a part of the Philippines despite its commitment, contained in the 1951 mutual defense treaty, to defend that country. It is apparent that the White House, the maker of China policy, was trying to placate Beijing.

The surrender of the Sudetenland did not work in 1938, and neither did the abandonment of Scarborough in 2012. Once they took that reef, the Chinese, in the second half of last year, began to increase pressure on Second Thomas Shoal. The United States, trying to keep the peace, unintentionally taught the region that aggression works, so why wouldn’t Beijing continue its tactics?

In the meantime, Washington hopes to calm the situation over Second Thomas Shoal. “This is a provocative move that raises tensions,” said State Department spokeswoman Jen Psaki on Wednesday, referring to the Chinese blocking of the Philippine ships. “Pending resolution of competing claims in the South China Sea, there should be no interference with the efforts of claimants to maintain the status quo.”

Her mild comment did not make Chinese hearts beat faster. American words are now a debased currency in East Asia. Too much has been said, and too little has been done. Admiral Jonathan Greenert, chief of naval operations, declared in the middle of last month that the U.S. would “help” the Philippines if China occupies its islands, but Manila knows the Chinese are already stationed on Mischief Reef, which Beijing took from Manila in 1995, as well as sailing around Scarborough. Washington did little to assist in either case. Aquino and the Filipinos are bound to hear soaring rhetoric when President Obama visits Manila next month, but what they need now is American action, such as clearing away the Chinese vessels ringing the Sierra Madre.

American nuance is no longer working in East Asia. The Chinese will soon force U.S. policymakers to make a clear choice, either to acquiesce to Beijing’s aggression or protect its allies and friends. That, of course, is a choice Washington has been trying to avoid making for two decades. But sooner or later—sooner is better—America and the region’s threatened democracies will need to band together. In 2006, Taro Aso, then Japan’s foreign minister, proposed an “arc of freedom and prosperity” for the region. The idea went nowhere as Washington and other capitals were bent on engaging the Chinese.

Now, however, engagement in substance looks no better than appeasement and democracies are threatened by Beijing. Aso’s grand idea is the perfect architecture for our ominous-looking times.

Now it is evident that the Chinese are not going to stop taking territory until they are stopped. Hitler was not happy with just a portion of Czechoslovakia, and the Chinese were not satisfied with only a piece of the Philippines.

The Sudetenland solution, Washington should have known, never works.

Gordon G. Chang is the author of The Coming Collapse of China. Follow him on Twitter @GordonGChang (http://twitter.com/GordonGChang).