The US and the UK have carried out military strikes with aircraft, ships and missiles against targets linked to the Houthi rebels in Yemen.
The attacks came after the Houthis launched their largest attack yet on Red Sea shipping, one of 27 such assaults since 19 November.
Officials said that 21 missiles and drones were fired at warships and commercial vessels near the Bab al-Mandab Strait early last week, the southern bottleneck of the Red Sea, with US and UK warships blowing them out of the sky.
Since the US-UK strikes, the Iranian-backed Houthis have vowed to expand their Red Sea raids to include US ships, and successfully struck an American-owned cargo vessel off Yemen on Monday night.
“The ship doesn’t necessarily have to be heading to Israel for us to target it; it is enough for it to be American,” Nasruldeen Amer, a spokesperson for the Houthis, told Al Jazeera. “The United States is on the verge of losing its maritime security.”
Here is what we know so far:
What targets were hit in the strikes?
The US said that it carried out strikes at more than 60 targets at 28 Houthi locations, with the Pentagon saying that radar systems, drone and missile storage and launch sites, plus Houthi command centres were all hit. Strikes were reported in the Yemen capital Sanaa - which is controlled by the rebels - as well as the Houthi Red Sea port of Hodeidah, Dhamar and the group's north-western stronghold of Saada.
Britain’s Ministry of Defence (MoD) said that it had identified key facilities involved in Houthi targeting of HMS Diamond and US Navy vessels earlier this week "and agreed to conduct a carefully coordinated strike to reduce the Houthis' capability to violate international law in this manner".
It said fighter jets conducted precision strikes on two of these Houthi facilities. "One was a site at Bani in north-western Yemen used to launch reconnaissance and attack drones. A number of buildings involved in drone operations were targeted by our aircraft. The other location struck by our aircraft was the airfield at Abbs. Intelligence has shown that it has been used to launch both cruise missiles and drones over the Red Sea. Several key targets at the airfield were identified and prosecuted by our aircraft.”
The Houthis said there were more than 70 strikes in total.
How have the Houthis responded?
The Houthis have continued to target ships since the US-UK strikes, saying that as well as Israel-linked vessels they now see British and American ships as legitimate targets.
The US military said it repelled a missile attack on one of its warships over the weekend, an anti-ship cruise missile that was fired by the rebels towards the USS Laboon in the Red Sea. It was drowned by a US fighter jet off the coast of Hodeidah.
And the Houthis also claimed responsibility for a missile attack on a US-owned cargo ship off the south coast of Yemen on Monday 15 January. The attack involved three missiles, one of which struck the Gibraltar Eagle and caused a fire.
The United Kingdom Maritime Trade Operations (UKMTO), which oversees Middle East waters, issued an advisory to all vessels in the region and urged caution during transit through Red Sea.
The assaults have prompted prominent shipping firms to reroute ships from the Red Sea, opting for a more extended journey around southern Africa instead.
On Monday, QatarEnergy, the second-largest oil company globally, declared a temporary halt to shipping through the route as it sought security guidance.
What weapons did the US and UK use?
US Navy warships fired Tomahawk land attack cruise missiles, which are GPS-guided and can be programmed to fly evasively, the US military says.
While no specific figures have been given for how many missiles were fired, the US says more than 100 precision-guided munitions "of various types" were used.
The UK said it sent four RAF Typhoons from Cyprus, carrying Paveway IV guided bombs. It has not said how many were released. The two UK Navy warships in the Red Sea cannot fire land attack missiles, hence the need for aircraft.
The UK and US had non-operational support from Australia, Bahrain, Canada and the Netherlands.
Who are the Houthis and why are they attacking in the Red Sea?
The Iran-backed Houthis armed group from a sub-sect of Yemen's Shia Muslim minority, the Zaidis. They take their name from the movement's founder, Hussein al-Houthi. They have been fighting a civil war since 2014 against Yemen's government. The government has been backed against the Houthis by a coalition of Arab countries led by Saudi Arabia and the UAE.
The Houthis are part of what Tehran labels an “axis of resistance” against Israel, the US and the wider West which includes Hamas and Hezbollah from Lebanon. A Hamas attack inside Israel on 7 October that killed 1,200 people and saw 240 taken hostage triggered Israel to bombard Gaza aiming to eradicate the group. Health officials in the Hamas-run territory say the Israeli military operation has killed more than 23,000 people. The Houthis claim they are targeting all ships bound for Israel through the Bab al-Mandab Strait in support of the Palestinian people.
The Houthis subsequently began targeting commercial vessels indiscriminately, triggering the mobilisation of a US-led naval coalition at the end of last year to counter this threat.
The Houthis have launched a number of attacks since November, carrying out at least 27 attacks on cargo ships in the Red Sea.
Why is the Red Sea important?
It is one of the major waterways for global trade; roughly 12 to 15 per cent of shipping traffic passes through the Red Sea.
Many shipping companies have been forced to reroute their vessels, taking the longer journey around Africa, although several oil majors, refiners and trading houses have continued to use it.
Alternative routes cause delays in supply chains, while increased insurance costs for sailing through the Red Sea threaten to have a knock-on effect to end costs.
Insurance premiums roughly doubled in the wake of the Houthi attacks.
German shipping group Hapag Lloyd said on Tuesday it would continue to avoid the Suez Canal and go around the Cape of Good Hope for security reasons, while its Danish rival Maersk has said it would avoid the route “for the foreseeable future”.
Thus far, spikes in energy prices as a result of the attacks have been short-lived and increased insurance costs have remained manageable, but experts have warned that if a few ships were sunk by a future assault, the situation could worsen.
What have Joe Biden and Rishi Sunak said about the strikes?
President Biden said the strikes were in "direct response" to the Houthi attacks in the Red Sea. "These attacks have endangered US personnel, civilian mariners, and our partners, jeopardised trade, and threatened freedom of navigation," he said.
Mr Sunak said that the action was "necessary and proportionate" to protect global shipping.
"Despite the repeated warnings from the international community, the Houthis have continued to carry out attacks in the Red Sea, including against UK and US warships just this week," he said. "This cannot stand."
Could the attack escalate regional tensions?
A spokesperson for the German foreign ministry said the latest Houthi attacks showed the militant group were “clearly focusing on escalation against international merchant shipping”. Before the US and UK airstrikes, British defence secretary Grant Shapps described the situation in the Red Sea as unsustainable and said that the HMS Diamond, the British warship stationed in the area, had been specifically targeted in the latest attack.
The Houthis have vowed to continue their assaults until Israel halts the conflict in Gaza, and warned they would attack US warships if the militia group itself was targeted.
Mohammed al Bukhaiti, a senior Houthi official, wrote on X in December: “Even if America succeeds in mobilising the entire world, our military operations will not stop... no matter the sacrifices it costs us.” But the Houthis have no formal naval warships with which to impose a serious blockade of the waterway, while the defence capabilities of the coalition forces are more than able to cope with the threat of drones and missiles.
However the UK and the US have had to weigh their determination to keep the shipping lane open against the risk of spreading war in the region. The strikes were the first by the United States on Yemeni territory since 2016, and the first time it has attacked the Iran-backed Houthis at any such scale.
Saudi Arabia called for restraint and "avoiding escalation" as it looks to withdraw from the civil war in Yemen. The conflict has lately been in a delicate state of UN-backed peace negotiations. Saudi Arabia have been anxious about any response from the US and others that could complicate those efforts.
