The Houthis continue to confound some of the world's most powerful militaries. They are still firing missiles at any international shipping they consider linked to the US, UK or Israel, as well as some that isn't.
They have already had a major impact on global trade, forcing ships to divert thousands of miles away. They seem undaunted by repeated US-led airstrikes on their missile bases and they have vowed to retaliate against US and UK assets.
So just who are the Houthis, how did they get so powerful and what happens now in the Red Sea?
Who are the Houthis?
The Houthis are a minority group of Yemenis from the mountainous northwest of the country.
They take their name from their movement's founder, Hussein Al-Houthi. They fought several wars against Yemen's strongman ruler in the early 2000s and then, after he was deposed by the Arab Spring protests, they marched down to the capital, Sana'a, and seized power in 2014. The previously deposed President Saleh, still bitter at being ousted, put his loyal Republican Guard at their disposal, enabling them to take over 80 per cent of Yemen's population.
The Houthis then promptly assassinated him.
Since the Houthis seized power Yemen, already the poorest Arab nation, has been torn apart by a catastrophic civil war.
An estimated 150,000 people have been killed, along with millions made dependant on food aid. For seven years the Houthis survived a massive and ultimately fruitless coalition air campaign to oust them, led by the Saudis who were alarmed at the Houthis' links to their arch-rival, Iran.
"The Houthis embody a triumphant mindset, forged through a series of victories over two decades", says Mohammed Al-Basha, a Middle East expert with the Virginia-based consultancy Navanti.
"Demonstrating resilience from 2015 to 2022, they effectively thwarted the Saudi-led coalition's attempt to reinstate the internationally recognised government in Sana'a."
From mid-November 2023 onwards, the Houthis have used their substantial arsenal of missiles and drones to target shipping passing close to the narrow, strategic chokepoint of the Bab Al-Mandeb Strait.
Their stated aim was to attack any vessel with Israeli links, in support of Hamas, vowing to continue their attacks until Israel ends its own assault on Gaza. When US and British warships came to the defence of container vessels steaming past Yemen's Red Sea coast the Houthis directed their attacks on the warships, at one point losing three of their speedboats and 10 sailors in a one-sided engagement with the US Navy.
Despite that loss, attacking the US Navy and Royal Navy, says Mohammed Al-Basha, "underscores the Houthis' prevailing sense of triumph and fosters euphoric hubris within their ranks.. leading some members of the group to perceive divine intervention and a historic alignment in their favour."
The Houthis - most of whom follow the Zaidi branch of Shia Islam in Sunni-majority Yemen - represent only around 15 per cent of Yemenis yet they consider themselves the rightful rulers.
So how do they differ from the rest of the population?
'Houthis are war-like, violent and cruel'
"They are generally more war-like, violent and cruel" says Edmund Fitton-Brown, who was UK ambassador to Yemen from 2015-17.
"I encountered astonishing instances of brutality in Aden and Ta'izz. The Houthis consider themselves an elite from an elite (the Zaidi sect). Some of their casual viciousness towards Sunni civilians in central and southern Yemen has been remarkable: a readiness to deploy snipers and kill non-combatants for fun."
There has long been a concerted effort, led by the UN, to end Yemen's civil war and the Saudis, who host the legitimate but ousted Yemeni government, have concluded a fragile truce with the Houthis.
Edmund Fitton-Brown had some experience of dealing with them in negotiations.
"It was extremely challenging", he says.
"They were difficult, hostile, capricious, prone to tantrums, late arrivals and walkouts. They insisted on VIP treatment and a ready supply of qat [a narcotic leaf chewed by many Yemenis]. During peace talks they drove their Kuwaiti hosts mad with frustration."
Since the Houthis began their attacks on shipping, and the US and UK responded with air strikes on their missile bases, there have been vast, government-sanctioned protests against the West in the capital.
So how genuine are they?
"By opposing what many in the population of northern Yemen perceive as foreign forces, including the US, UK and the Saudi-led coalition, and directly confronting Israel in support of Gaza" says Al-Basha, "the Houthis have gained popularity."
He adds however, that present-day Yemen remains a divided nation, with anti-Houthi resistance persisting in pockets of north-eastern Yemen, Ma'rib, Tai'izz and the southern governates. It appears unlikely the Houthis could emerge victorious in a "free and fair election".
As to the protests, Fitton-Brown says the Houthis bring out mobs on the street through fear.
"They call a demonstration, make it a holiday from work, make it clear that attendance is expected. Many of their personnel were recruited because they were unemployed and desperate to earn a wage. In areas outside their control they are loathed."
And meanwhile the missiles keep coming.
The Houthis seem to have an almost inexhaustible supply of drones and other munitions to launch at shipping, much of it supplied by Iran with parts smuggled in at sea in small boats or across the desert border with Oman.
How does this end?
Doubtfully with the Houthis capitulating.
"They won't want to lose face" says Fitton-Brown.
"But [if a ceasefire occurred in Gaza] they may seize an opportunity to declare victory, claiming that they have achieved their objectives. If Iran becomes concerned that Houthi actions are putting the Islamic Republic at risk they have enough influence to make the Houthis look for a way out."
So for now, the situation in the southern Red Sea is a standoff.
The Houthis are not backing down under military pressure, despite seeing one after another of their missile launch sites destroyed by US-led airstrikes. They clearly have plenty more in their arsenal and the indications are they are looking to raise the stakes by preparing surface-to-air missile sites with a view to shooting down a western warplane.
The southern Red Sea and adjacent Gulf of Aden will remain a dangerous part of the world for the foreseeable future.
