South China Sea

Two Chinese fighter jets conducted an "unprofessional" intercept of a U.S. aircraft in international airspace over the East China Sea on Wednesday, according to the U.S. Air Force.

The American aircraft was conducting a routine mission in accordance with international law when the two Chinese SU-30 jets made the move, Pacific Air Forces spokeswoman Lt. Col. Lori Hodge told NPR.

Chinese officials smashed a bottle of Champagne on the bow of their second aircraft carrier Wednesday, launching what the Defense Ministry calls the country's first "homemade" carrier — which took less than four years to build.

The as-yet-unnamed carrier joins the Liaoning, a repurposed 1980s-era Soviet ship that was bought from Ukraine and launched in 2012. Together, the Chinese ships represent a new dimension in the increasingly crowded waters in and around Asia, where claims and counter-claims have been made on islands and shipping routes.

"We try to be friends with everybody, but we have to maintain our jurisdiction," Philippine President Rodrigo Duterte said Thursday, describing his order for troops to fortify islands that his country has claimed in the South China Sea.

The order applies to a group of islands in the western portion of the Spratly Islands.

"There's so many islands," Duterte said. "I think nine or 10."

After President-elect Donald Trump's pick for secretary of state made strong statements about China's actions in the South China Sea, Chinese officials have responded with muted, measured statements — while state-run media have warned of the potential for conflict and retaliation.

Rex Tillerson, the former Exxon Mobil CEO nominated to lead the U.S. State Department, had a confirmation hearing Wednesday. He told the Senate Foreign Relations Committee that China's actions in the South China Sea were "extremely worrisome" and compared them to Russia's annexation of Crimea.

As part of the project A Nation Engaged, NPR and member stations are exploring America's role in the world heading into the presidential election.

On Tuesday, an international tribunal soundly rejected Beijing's extensive claims in the South China Sea, an area where China has been building islands and increasing its military activity.

The case before the international tribunal in the Hague was brought by the Philippines, challenging what's widely seen as a territorial grab by Beijing. The tribunal essentially agreed. Beijing immediately said the decision was null and void and that it would ignore it. There are concerns now that the tribunal's decision could inflame tensions between the U.S. and China.

An international tribunal in The Hague has invalidated China's claims in the South China Sea in a first-ever ruling. The decision has been rejected by Beijing.

The disputed waters are claimed by China, Taiwan, Malaysia, the Philippines, Vietnam and other countries. But China has been the most aggressive in staking out its claim — marking a "nine-dash line" around the bulk of the islands and waters, and building up artificial islands within the disputed region.

The dispute over the South China Sea, one of the most complicated geopolitical issues of the 21st century, keeps heating up. China, Taiwan, Malaysia, the Philippines, Vietnam and other regional governments are all part of the dispute — along with the United States.

Here are four key things to know about the dispute.

1. What's At Stake

The South China Sea holds immense resources, from the oil and gas located underneath the seabed to the lucrative fishing it has afforded for generations.