A top U.S. commander said China has fully militarized at least three islands it built in the South China Sea, reneging on promises it made and escalating tensions with surrounding nations. “I think over the past 20 years we’ve witnessed the largest military buildup since World War II by the [People’s Republic of China,]” Adm. John C. Aquilino told the Associated Press. “They have advanced all their capabilities and that buildup of weaponization is destabilizing to the region.” The islands have been equipped with anti-air and anti-ship missile systems, jamming technology, and fighter jets. China did not immediately comment on the U.S. claim, though the country previously said it would not militarize the islands in the disputed region. The revelation was disclosed as journalists boarded a U.S. patrol jet in the South China Sea, which was threatened by the Chinese military as they were on board.