Russia has tested a new hypersonic missile that can penetrate any enemy defense, the Kremlin claimed. 

But foreign military planners probably shouldn't panic. The Kremlin might be exaggerating the effectiveness and usefulness of its new weapon.

On Dec. 26, 2018, Russian president Vladimir Putin announced that the Russian military had tested the Avangard hypersonic glide vehicle in order to "successfully verify all of its technical parameters," state-owned TASS news agency reported.

"On my instructions the industrial enterprises and the defense ministry have prepared for and carried out the final test of this system," Putin said, according to TASS. "The test was completely successful: all technical parameters were verified."

Avangard is what the U.S. military calls a “hypersonic glide vehicle.” Propelled to high speed by the same kind of rocket that boosts a satellite or a intercontinental-range nuclear warhead, a hypersonic glide vehicle follows a different kind of flight path than other payloads do.

Anything faster than five times the speed of sound qualifies as "hypersonic."

Staying relatively close to Earth — around 300,000 feet up, approximately where the atmosphere ends and space begins — a hypersonic vehicle glides toward its target at many times the speed of sound, potentially performing small maneuvers en route.

In theory a hypersonic glide vehicle can carry a conventional explosive warhead, a nuclear warhead or no warhead at all, instead relying on sheer kinetic force to destroy its target. Its low altitude and high maneuverability compared to a traditional intercontinental ballistic missile could make it harder to intercept.

"We don't have any defense that could deny the employment of such a weapon against us," Gen. John Hyten, commander of U.S. Strategic Command, told the Senate Armed Services Committee in March 2018.

But ICBMs already are capable of blasting through normal defenses. The United States and Russia both possess missile-interceptors they claim can hit incoming ICBMs, but experts question the interceptors’ effectiveness against such fast targets.

The U.S. Army's Ground-Based Midcourse Defense missiles in Alaska and California represent America's main defense against nuclear-armed ballistic missiles. But the GMD rockets lack the speed, maneuverability and accuracy to hit an ICBM, which in its final phase of flight can reach a velocity 20 times the speed a sound.

The U.S. Missile Defense Agency claimed the GMD system intercepted a "complex, threat-representative ICBM target" during a May 2017 test. But experts claimed the test was unrealistic. "The Missile Defense Agency simplified the test to enhance its chances of succeeding," said Laura Grego, a missile expert with the Union of Concerned Scientists in Massachusetts.

If American defenses can't hit an ICBM, they probably also would fail to hit a Russian hypersonic glide vehicle. But that might not matter, if Moscow intends to deploy Avangard or another hypersonic vehicle as a strategic weapon carrying a nuclear warhead.

No country has ever possessed a reliable defense against a long-range strategic weapon. Instead, nuclear states count on the threat of atomic counterattack -- "mutual assured destruction" is the Cold War term -- in order to deter a nuclear attack.

Avangard could become just another strategic weapon that that United States counters with strategic weapons of its own. "Our response would be our deterrent force, which would be the triad and the nuclear capabilities that we have to respond to such a threat," Hyten said.

Hypersonic weapons might be more useful, and more effective, if they do not carry nuclear warheads. In July 2018, Michael Griffin, the U.S. Defense Department's undersecretary of defense for research and engineering, warned about the "tactical capability that these sorts of weapons bring to theater conflicts or regional conflicts."

Griffin characterized hypersonic vehicles as "very quick response, high speed, highly maneuverable, difficult to find and track and kill."

Putin claimed Russian forces would deploy Avangard as early as 2019, potentially making Russia the first country to field, on an operational scale, a practical, non-nuclear hypersonic weapon. China and the United States continue to develop hypersonic weapons of their own, but so far have declined to issue the weapons to front-line forces.

In rushing to be first, Russia could end up fielding an unreliable weapon. In July 2018, Griffin asserted that the United States remained the world leader in hypersonic-weapons research. The Pentagon determined there was no need to hurry up and equip troops with an unrefined weapon.  "We didn’t see a need for it."

America's hypersonic weapons would mature "through the 2020s," Griffin said. “You’re going to see our testing pace stepping up, and you’re going to see capability delivery from the early '20s right through the decade."

Griffin also cast doubt on the Kremlin's bold claims regarding its own super-fast weapons. "How close they are to operational, I just don’t know."