A Houthi missile recently put a US destroyer's close-in weapons system to the test, a report said.
A warship's CIWS is usually considered its last line of defense and is for close-range intercepts.
The Tuesday incident marks the latest Houthi missile attack, though not the latest exchange of fire.
A Houthi anti-ship cruise missile fired into the Red Sea came within a mile of a US Navy destroyer on Tuesday, a report said, close enough that the American warship turned to its close-in weapons system — a last line of defense.
Most missiles are shot down farther out. This was the closest that a Houthi attack had come to an American warship, four US officials told CNN, which reported additional details of the incident on Wednesday.
US Central Command initially said on Tuesday that around 11:30 p.m. local time, the Houthis fired a single anti-ship cruise missile from Yemen toward the Red Sea, and it was shot down by USS Gravely.
There was no reported damage or injuries. Centcom declined Business Insider's request for additional information on Tuesday's missile downing.
For several months, the Iran-backed rebels have relentlessly fired one-way attack drones and missiles into key waterways off the coast of Yemen. Many of these threats have been shot down by US warships — and sometimes by British or French forces — though some of the munitions have struck commercial vessels transiting the region. No warships have been struck.
US Arleigh Burke-class destroyers are equipped with at least one CIWS, which features a close-range, radar-guided automatic 20 mm cannon that can fire up to 4,500 rounds a minute and has an effective range out to about two nautical miles.
Before a ship's CIWS is engaged, capabilities such as the warship's SM-2 or SM-3 interceptors come into play. These are fired from vertical-launch-system cells before they then intercept and destroy airborne threats. An SM-3 "hits threats with the force of a 10-ton truck traveling 600 mph," according to Raytheon, the weapon's manufacturer.
Warships can also use a chaff mechanism, which confuses a missile's radar.
The incident involving USS Gravely came just hours before US forces struck and destroyed a Houthi surface-to-air missile that was prepared to launch in Yemen and "presented an imminent threat" to American aircraft in the region, the military said on Wednesday.
The US has carried out several rounds of preemptive strikes this month targeting Houthi missiles — mostly the anti-ship capabilities — as the rebels were preparing to launch, posing a threat to commercial vessels and American warships off the coast of Yemen.
In addition to these preemptive actions, the US and UK have also conducted widespread strikes across Yemen, targeting Houthi sites such as missile launchers, weapons-storage facilities, radars, and air-defense systems.
Western officials have stressed that these strikes are a direct response to the Houthis' ongoing attacks against commercial vessels transiting the Red Sea and Gulf of Aden — a key global trade route — and that they will continue unless the rebels cease the provocations.
"We're certainly taking aggressive action against the Houthis to try to defend shipping in the Red Sea," John Kirby, the White House National Security Council spokesperson, said this week. He stressed, though, that the US was "not at war" with the Iran-backed rebels.
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