Suppose you’re a rising superpower with your eye on some ocean territory, but all the good islands are taken. China has been taking the latter option, dredging millions of tons of rock and sand and piling it on top of submerged reefs in the South China Sea. Vietnam, the Philippines, Taiwan, and Malaysia all control islands in the South China Sea, which is believed to hold large deposits of oil and natural gas. In 2012, China declared the region a core national interest, and it has been increasingly aggressive in asserting control over it, deploying an aircraft carrier in 2013, and moving an enormous oil rig into the area earlier this year.