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A deadly clash in the Red Sea that involved US helicopters, armed guards on a commercial ship and Houthi militias, left ten militiamen dead on Sunday.
In another sign of the simmering conflict in the region, Houthis launched three anti-ship ballistic missiles at the commercial vessel, the Maersk Hangzhou, a Singapore-flagged container ship.
One missile struck the vessel, causing damage but no casualties, while two of the missiles were shot down by the USS Gravely. The US said on Sunday that a naval task force created last month to protect shipping had shot down four ballistic missiles and 17 drones fired by the Iran-backed militia.
The naval vessel responded to the Maersk Hangzhou's distress call after the militias in boats shot at the ship from about 20 metres, a statement from Centcom, the US military headquarters for the Middle East, said.
It also described how “a contract embarked security team,” exchanged fire with the boats, while distress calls were made. Many shipping companies transiting the Red Sea now pay private security companies such as Ambrey to guard their vessels with armed contractors.
Helicopters, reportedly from the 100,000-tonne Dwight D Eisenhower aircraft carrier responded to Houthi fire during the clash, destroying three of the boats “in self-defence,” Centcom said.
Boat swarms and missiles
About 12 per cent of global seaborne trade transits through the Red Sea.
On Sunday, UK Defence Minister Grant Shapps issued a strong warning to the Houthis, saying the UK – part of an international task force to protect shipping – was considering “direct action,” in response to the group.
It also sheds light on the evolution of US countermeasures to “boat swarms,” which have long been feared by the US Navy operating in narrow waterways, particularly the Strait of Hormuz, where Iran operates armadas of small, missile-equipped fast boats.
The US concern stems from a military exercise in 2002, the Millenium Challenge, which saw an imaginary US opponent in the region – loosely based on Iran or Saddam Hussein-led Iraq – swarm US ships with explosive-laden attack boats, “sinking” 19 US vessels.
Since then, the US has reconfigured several weapon systems designed in the Cold War.
The Centcom statement did not say which weapons were used against the Houthi boats but the helicopters responding to the distress call were Sikorsky SH-60 Seahawks, which in addition to machine guns, can carry several missiles and rockets modified for naval use.
The SH-60 can carry a variant of the Hellfire missile, designed to destroy Soviet tanks, but tested in 2015 with a series of modifications to hit “high-speed manoeuvring surface targets,” according to a 2016 US army report, which said the weapon had a fragmentation warhead to destroy “boats in swarm attacks”.
The SH-60 can also carry 70mm rockets modified with the Advanced Precision Kill Weapon System, or APKWS.
How could Houthi attacks in the Red Sea affect global trade?
The 70mm rockets, used extensively in conflicts dating back to the Vietnam War, have been modified with laser guidance and were successfully tested in 2013 against fast-moving boats. The APKWS, according to a US Naval War College study, represents one of the cheaper options for tackling small boats, at about $20,000 per missile and can also be mounted on naval vessels.
Another ship-mounted missile, the BGM-176B Sea Griffin, has been extensively tested against small boats, with a range of up to 15km, but is more costly, at about $150,000 per missile.
US aircraft can also be fitted with guided cluster bombs against the boats, while anti-missile systems such as the Phalanx, which fires thousands of canon shells per minute, have also been adapted to fire at surface vessels.
For much larger threats, like anti-ship ballistic missiles and even low-flying cruise missiles that the Houthis possess, US warships are equipped with the Aegis defence system.
The heavily upgraded system that entered service in 1981 has proven adept at shooting down fast-moving ballistic missiles and can now counter complex attacks, involving different weapons used at once, designed to overwhelm defences.
Last month, US naval forces in the Pacific conducted an exercise with the Aegis system against ballistic missiles and mock cruise missiles, shooting down the targets in a simulated simultaneous attack, with two different types of interceptor missiles.
