The Taiwanese government maintains de facto control over the islands of Pratas and Itu Aba (which it calls Dongsha and Taiping) where it has stationed several hundred coast guard personnel for more than 20 years.

In doing so, Taiwan replaced detachments of marines in a move that signaled its willingness to de-escalate tensions in the contested waters. Taiwan’s defense minister, Chiu Kuo-cheng, said Taipei had no intention of deviating from this position.

Pratas is also claimed by China, while Taiping’s claimants include China, Vietnam and the Philippines. But only one—namely Beijing—has spent half a decade turning its South China Sea features into military bases, from which major naval and aerial operations can be conducted.

Over the weekend, the Associated Press reported China’s full militarization of Mischief Reef, Subi Reef and Fiery Cross Reef.

During a South China Sea patrol with Admiral John Aquilino, who commands American forces in the Pacific, the official described what he believed was China’s “largest military buildup since World War II.”

It included anti-ship and anti-aircraft missile systems, as well as lasers, electronic jamming equipment, and some fighter aircraft, he told the AP on Sunday.

The weaponry poses a threat to the one-third of global shipping that passes through the energy-rich sea, over which China claims a “historic right” via its oft-cited “Nine-Dash Line.”

Asked about a possible response by Taiwan, given Itu Aba’s proximity to China’s fully weaponized reefs, Chiu told the island’s legislators that the government would stay the course.

“The reason why everyone has been able to maintain … mutual non-aggression is because of the tacit observation of one rule: don’t attack me, and I won’t attack you,” he said at a parliamentary hearing in Taipei.

“[China] has its own militarization objectives. China has ambitions in the South China Sea, because it believes it has a right to all of it, so it has added some military installations,” he said.

“What we can do, like on Taiping Island, is deploy non-military garrisons, members of the coast guard. What’s the significance of this? To let everyone know that it’s not a militarized facility. Its focus is the maintenance of maritime safety in a peaceful manner,” said Chiu.

According the Asia Maritime Transparency Initiative (AMTI), a project under Washington’s Center for Strategic and International Studies think tank, the elliptic Itu Aba, which is 1,000 miles from Taiwan’s southwest port city of Kaohsiung, is the largest among the Spratly Islands.

Meanwhile, Pratas Island, 280 miles from Taiwan proper, was designated an atoll national park in 2007.

“Though it has generally focused on keeping the coral reef system surrounding Itu Aba pristine as an example of environmental conservation in the disputed waters, Taiwan did reclaim about eight acres of land to construct a new wharf, which was completed in late 2015,” AMTI’s island tracker said.

In September 2015, during a state visit to the United States, Chinese President Xi Jinping made a public commitment not to militarize artificial islands in the South China Sea. On Tuesday, China’s Foreign Ministry said it was “naturally entitled to deploy necessary defense facilities on its own territory.”

Aquilino said China’s militarized reefs served to “expand the offensive capability” of its military behind the country’s shores. “They can fly fighters, bombers plus all those offensive capabilities of missile systems.

“So that’s the threat that exists, that’s why it’s so concerning for the militarization of these island. They threaten all nations who operate in the vicinity and all the international sea and airspace,” he told the AP.