WASHINGTON >> After an international tribunal in The Hague, Netherlands, ruled emphatically against China in a territorial dispute with the Philippines, many Chinese state media outlets responded Wednesday by publishing a map. It showed the South China Sea, with most of the waters encircled with the “nine-dash line” that has long represented its claims there.

This week’s ruling may have delivered a sweeping victory in court to the Philippines, which argued that its maritime territory was being illegally seized by China. But it has only escalated the larger dispute, which involves several Asian nations as well as the United States, and which is as much about China’s rise into a major world power as it is about this one sea.

What follows is an explanation of why this body of water is considered such a big deal, and why it may be a harbinger of global power politics in the decades ahead.

Question: What is the dispute about?

Answer: At its most basic level, this a contest between China and several Southeast Asian nations over territorial control in the South China Sea, which includes some of the most strategically important maritime territory on Earth.

China, for the past few years, has been asserting ever greater control over faraway waters that were previously considered international or were claimed by other countries. For example, it has seized small land formations or reefs, sometimes dredging up underwater sediment to make the islands large enough to support small military installations.

China’s naval forces have also grown more aggressive in patrolling these claims and chasing off non-Chinese ships. That is part of why its neighbors see this as an effort by China to dominate the region.

This is also about whether China will comply with international laws and norms, which Beijing sometimes views as a plot to constrain the country’s rise.

The United States has gotten involved, sending the Navy to patrol waters it insists are international and backing international mediation efforts. Washington says it wants to maintain free movement and rule by international law. The risk of outright conflict is extremely low, but the militarization of these heavily trafficked and heavily fished waters is still dangerous.

Q: What does this week’s ruling mean?

A: The tribunal ruled almost categorically in favor of the Philippines, which had challenged some of China’s territorial claims. It also said China had broken international law by endangering Philippine ships and damaging the marine environment.

Maybe most important, the tribunal largely rejected the nine-dash line that China has used to indicate its South China Sea claims. This could open the way for other Asian states to challenge China’s claims.

So the letter of international law seems to say that China could be compelled to abandon many of its South China Sea claims.

But while the ruling is considered binding, there is no enforcement mechanism. China boycotted the proceedings, saying that the tribunal had no jurisdiction and that it would ignore any decision — a position it reiterated after the ruling came out.

Still, China is facing international pressure. Whether China chooses to defy or comply with that pressure, though, could help to shape its place in the international community.

Q: What is the ‘nine-dash line’?

A: This little line has shown up on official Chinese maps since the 1940s (it began with 11 dashes). It demarcates a vast but vague stretch of ocean from China’s southern coast through most of the South China Sea.

China has never clarified the line’s exact coordinates. But it sweeps across waters — and some small islands — that are claimed by five other nations. It seems to go many miles beyond what is allowed under the United Nations treaty on maritime territorial issues, which China signed.

These are the areas where China has been building islands, installing runways and running patrols.

For China, the line represents long-lost historical claims that the country, after two centuries of weakness, is finally strong enough to recover. For the other nations, the line is a symbol of what they characterize as a naked power grab by China.

Q: Why is the South China Sea so important?

A: The U.S. Energy Information Agency estimates there are 11 billion barrels of oil and 190 trillion cubic feet of natural gas in deposits under the sea — more than exists in the reserves of some of the world’s biggest energy exporters.

The waters also contain lucrative fisheries that account for, according to some estimates, 10 percent of the global total. But this means that a lot of fishing boats are cruising around in waters contested by several different navies, increasing the risk of conflict.

The area’s greatest value is as a trade route. According to a 2015 Defense Department report, $5.3 trillion worth of goods moves through the sea every year, which is about 30 percent of global maritime trade. That includes huge amounts of oil and $1.2 trillion worth of annual trade with the United States.

Q: Why does it matter who controls those trade routes?

A: This gets to a core contradiction in the South China Sea dispute: It is driven by territorial competition, yet all countries involved want open sea routes. Everyone benefits from the free flow of goods between Asia and the rest of the world, and everyone suffers if that is disrupted.

This is part of why the United States stresses freedom of movement in international waters. While it is very unlikely that China would ever want to close off trade, the United States would still rather not allow Beijing even the ability to hold the global economy hostage.

But, from China’s perspective, the United States itself has that ability, because of American naval dominance; the Chinese also suspect that the global status quo is engineered to serve Western interests first. So it is hardly surprising that China is seeking greater control over waterways it relies on for economic survival.

This is a dynamic that has permeated Sino-American relations throughout China’s rise over the past two decades. In theory, both nations understand they are better off cooperating. But in practice, they often treat each other as competitors or potential threats — a cycle that is difficult to break.

Q: So this is about China’s rise?

A: In some ways, yes.

China sees itself as a growing power that has a right to further its interests in its own backyard, just as Western powers have done for centuries. Beijing considers the South China Sea an area of traditional Chinese influence, and sees its control as a way to assert greater power over the region.

Something Americans often miss is that for China, this is in part defensive. The history of Western imperialism looms large. Chinese leaders often distrust the United States’ intentions, and consider their country to be the far weaker party. Extending Chinese control is a way to stave off perceived threats.

This insecurity also contributes to Chinese skepticism of international institutions such as the South China Sea tribunal, which Chinese state media portray as a plot to weaken China.

Q: Why is the United States so involved in this?

A: The United States has a treaty obligation to the Philippines, an ally. As the world’s largest economy, it also has a real interest in maintaining open sea lanes — and, as the world’s biggest naval power, it often assumes the role of policing them. Plus, as the world’s only superpower, the United States often acts as a balancer in regional disputes.

But this is also, for Washington, about shaping what sort of major power China becomes.

American officials insist that they do not oppose China’s rise. Their concern is whether China will work within what scholars call the liberal order — the postwar system of international laws and institutions — or seek to overturn it.

The South China Sea, and particularly this week’s ruling, are a test case for whether China becomes the kind of power that works within that system, or against it.

While that order has helped promote peace and prosperity globally, it also undeniably serves American interests.

Everyone agrees that the status quo in Asia and eventually the world will evolve to accommodate China’s emergence as a major international power. The South China Sea is very important in its own right, but it is maybe most important in helping to determine what sort of role China plays in the world.

© 2016 The New York Times Company