Hypersonic Missiles Are a Game Changer

No existing defenses can stop such weapons — which is why everyone wants them.

Last week, President Vladimir Putin of Russia announced the deployment of the Avangard, among the first in a new class of missiles capable of reaching hypersonic velocity — something no missile can currently achieve, aside from an ICBM during reentry.

Whether or not the Avangard can do what Mr. Putin says, the United States is rushing to match it.