On Air Force fighter jets, magnets made of rare earth minerals that are mined or processed in China are needed to start the engines and provide emergency power.
On precision-guided ballistic missiles favored by the Army, magnets containing Chinese rare earth materials rotate the tail fins that allow missiles to home in on small or moving targets. And on new electric and battery-powered drones being adapted by Marines, rare earth magnets are irreplaceable in the compact electric motors.
China’s decision to retaliate against President Trump’s sharp increase in tariffs by ordering restrictions on the exports of a wide range of critical minerals and magnets is a warning shot across the bow of American national security, industry and defense experts said.
In announcing that it will now require special export licenses for six heavy rare earth metals, which are refined entirely in China, as well as rare earth magnets, 90 percent of which are produced in China, Beijing has reminded the Pentagon — if, indeed, it needed reminding — that a wide swath of American weaponry is dependent on China.
They are present in almost every form of American defense technology. They can form very powerful magnets, for use in fighter jets, warships, missiles, tanks and lasers. Yttrium is required for high-temperature jet engine coatings; it allows thermal barrier coatings on turbine blades to stop aircraft engines from melting midflight.
According to the Defense Department, every F-35 fighter contains around 900 pounds of rare earth materials. Some submarines need more than 9,200 pounds of the materials.
Across the American defense industry, aerospace and weapons companies have small stockpiles of the rare earths — the industry term for the 17 elements. That is enough, defense industry analysts say, to meet their needs for months rather than years.
The Pentagon also has stockpiles of some rare earths, but those reserves are not enough to sustain defense companies indefinitely, one official said.
China has flexed its muscle over the rare earth supply chain in the past. In 2010, Beijing halted rare earths trade with Japan following Japan’s detention of a Chinese fishing trawler captain. The Chinese move caught the attention of the United States, alerting it to the threat posed by China’s control over the minerals’ supply chain.
In 2017, during his first term, Mr. Trump signed an executive order aimed at boosting U.S. domestic production, and President Joseph R. Biden Jr. followed suit during his administration, allocating even more money for rare earth extraction and refinement facilities.