Hypersonic Missiles Are Game-Changers, and America Doesn’t Have Them

The weapon Beijing launched over the South China Sea traveled at speeds of more than 15,000 miles an hour as it circled the globe.

Flying at least 20 times the speed of sound, it could reach anywhere on earth in less than an hour. 

The summer 2021 test flight ended with the missile striking near a target in China, but it sent shock waves through Washington. National security officials concluded Beijing had launched a hypersonic weapon—a projectile capable of traveling at least five times the speed of sound.

The weapons...