Lightning Houthi advance in Yemen may bring dangerous new dimension to Iran war

"Now that they are there, they're going to be entrenched," Hisham al-Omeisi, senior analyst at the Brussels-based European Institute of Peace, told the BBC. "And it's going to be a lot more costly to push them out."

Of course, the Houthis are not alone. They enjoy the backing of Iran, support that has become even more important for Tehran in the wake of the setbacks and defeats experienced by other parts of its so-called "Axis of Resistance" – Lebanese Hezbollah, Hamas in Gaza and the Assad regime in Syria.

"So they redirected their support to the Houthis," al-Omeisi said. "And of course they need that support."

Even though most analysts agree that it's a mistake simply to describe the Houthis as Iranian puppets, events of the past few days raise an uncomfortable new reality.

Seven months after the US and Israel launched their huge, combined assault on Iran, the regime in Tehran now exerts authority over not just one, but two of the world's most important maritime passages: the Strait of Hormuz, at the mouth of the Persian Gulf, and the Bab al-Mandab, gateway to the Red Sea (and the Suez Canal).

"Now Iran, directly and through proxies, controls two of the most strategic choke points in the Middle East and the world," says Farea al-Muslimi, a research fellow at London's Chatham House think tank, "controlling more than 35% of the fuel and oil trade globally."

"This is as much leverage as a nuclear bomb," he says.

If the Houthis have also taken control of several key islands in the Red Sea, including Perim - which sits in the middle of the narrowest point of the Bab al-Mandab - then the group's ability to interfere with international shipping will be greatly enhanced.

As the group's actions in the wake of Israel's war on Gaza proved, shipping in the Red Sea is highly vulnerable to Houthi missiles, drones and small attack boats.

"They were able to control what was going in and out of the Bab al-Mandab and up towards Suez without having these territorial gains," Yemen expert Iona Craig told BBC Radio 4's Today programme on Friday.

"But of course now they're controlling the area immediately overlooking the Bab al-Mandab, and this gives them far more leverage."

Shipping companies are likely to be sceptical about the sincerity of a statement released on Friday afternoon, in which the Houthi military said that maritime navigation was "safe for all companies except for Saudi vessels, which have already been subject to a blockade".

In their earlier attacks, the Houthis said they were only targeting vessels linked to Israel, but in fact hit ships with no such connection, including a Norwegian-flagged tanker.

Craig said the Houthis may nevertheless refrain from indiscriminate attacks, fearing a repeat of Operation Rough Rider - six weeks of major US air and naval strikes in the spring of 2025.

"They've already felt the wrath of the US," she said.

But would the US want to get involved anyway?

President Donald Trump's war with Iran is already unpopular. With oil prices creeping back up, it's doubtful that a new front would do much to enhance his approval ratings or his Republican party's chances in November's midterm US elections.

According to the Axios website, appeals for US intervention from the Saudi Crown Prince Mohammed bin Salman have so far gone unanswered.

Axios writes that the US "is increasingly concerned about the escalating conflict in Yemen and is working to intensify its support for the kingdom while simultaneously seeking to avoid direct military involvement".

But it's not just the potential threat to the Bab al-Mandab that's causing fear in Saudi Arabia.

Satellite images of an apparent Houthi missile-and-drone attack on Saudi Arabia's East-West pipeline – a vital alternative route for oil exports following the closure of the Strait of Hormuz earlier this year – point to an effort by Iran's Yemeni allies to add to the economic pressures generated by the US-Israeli war with Iran.

Even if Iran did not directly order the attack, it clearly stands to benefit.

Baraa Shaiban, a researcher and analyst at the London-based Royal United Services Institute, says the origins of the latest upsurge in fighting – the worst since a United Nations-brokered truce in 2022 - can be traced back to July, when a Houthi delegation returned from the state funeral of Iran's Supreme Leader, Ayatollah Ali Khamenei.

"Immediately after, the escalation started," he says, "and it looked very clearly that [Iran was] determined to now have a bigger foothold on the Red Sea".

With Yemen teetering on the edge of a return to all-out war, Saudi Arabia anxious about preserving its economic lifeline to the Red Sea and Donald Trump apparently reluctant to get involved, America's conflict with Iran just took on a new and potentially dangerous dimension.

For the people of Yemen, displaced, bombed, starved and impoverished by a dozen years of civil war, recent developments can only make their lives worse.