China has done the same; in 2015 alone it created the equivalent of two Manhattans of new real estate. All told, according to a Dutch research group, human beings since 1985 have added 5,237 square miles of artificial land to the world’s coasts — an area about as big as Connecticut or the nation of Jamaica.

The process often entails enormous environmental damage. China recently suspended all commercial land reclamation projects because of the harm they were inflicting on coral reefs and coastal ecosystems. They have some experience with the issue; China dumped so much sand onto reefs in the Spratlys that one American marine biologist called it “the most rapid rate of permanent loss of coral reef area in human history.”

But of even greater concern is how China’s island building is serving its military ambitions. Almost as soon as the sand was dry on the Spratlys, China began building military bases. Beijing’s armed forces have installed antimissile weaponry, runways capable of handling military aircraft, structures that United States officials believe are designed to house long-range surface‑to‑air missile launchers, and port facilities that may be capable of accommodating nuclear submarines.

This expansion of China’s military power in the Pacific is an intensifying flash point between China, the United States, and its Pacific allies. At his confirmation hearings to become secretary of state, Rex Tillerson compared China’s Spratly buildup to Russia’s invasion of Crimea. In recent weeks, the United States has flown B-52s over, and sailed two warships past, the disputed archipelago.

For its part, China landed a long-range bomber on one of the newly made islands. In June, Defense Secretary Jim Mattis denounced China’s buildup as “intimidation and coercion.” President Xi Jinping responded that “we cannot lose even one inch of (our) territory.” All of which shows that in the 21st century, geopolitical power goes not only to those who control territory — but those who can manufacture it.