It took Houthi rebels less than 48 hours to seize Yemen’s Red Sea coast from pro-government forces in a resounding blow to U.S. interests and Washington’s regional allies.

But the Houthis didn’t do it alone. Iranian Revolutionary Guard advisers were in the field helping direct the battle, people familiar with the offensive told The Associated Press, marking Iran’s most direct intervention in favour of its longtime ally since Yemen’s civil war erupted in 2014.

The intervention shows how Iran has built the Houthis into a major regional partner able to open a new front in the wider war with the U.S.

The rebels’ biggest land grab in years, along with the closure of a key Saudi pipeline, strengthened their ability to choke off Saudi Arabia’s oil exports, pushing up global fuel prices and giving Iran greater leverage. The United States has seemed reluctant to help its ally Saudi Arabia, even as the Houthis have gained momentum in Yemen’s revived civil war.

The AP spoke to 10 officials and soldiers to assemble an account of the Houthi offensive. They included a senior Houthi official, two regional officials, a top Yemeni military commander and a member of Yemen’s ruling presidential council. They spoke on condition of anonymity to discuss internal decision-making.

The Houthis’ swift, 115-kilometre (75-mile) assault exploited divisions among forces allied with Yemen’s Saudi-backed, internationally recognised government. The Houthis penetrated the internal communications of one of the main forces, the National Resistance, allowing them to track its movements and sow confusion.

As pro-government forces beat a frantic retreat, the leader of the National Resistance fled to Saudi Arabia. The key port city of Mokha was abandoned as residents left in the night, allowing the Houthis to roll in unopposed on September 10. Their seizure of strategic islands nearby further enhanced their ability to attack Saudi oil shipments in the Red Sea.

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Iran had been building up the Houthis’ capabilities

The Houthis had not conducted a major campaign along the coast since 2017, when government forces drove them out of the area. Since then, the Houthis have focused on trying to capture the oil-rich province of Marib in central Yemen.

A truce took hold in 2022. The following year, the Houthis began attacking Red Sea shipping over the war in Gaza, attacks that continued until a punishing US bombing campaign in 2025. After the US and Israel attacked Iran in February, the Houthis largely kept to the sidelines.

Last year, Iran began providing the Houthis with stepped-up training and logistical support on more advanced missiles, drones and uncrewed attack boats, said Mzahem Alsaloum, a security analyst who has followed Iranian-backed groups for nearly a decade and now runs a private intelligence firm.

In July, the Houthis renewed their attacks on Saudi Arabia after accusing it of striking the airport in the rebel-held capital, Sanaa. That strike appears to have been aimed at halting a flight from Tehran.

Alsaloum and the senior Houthi official said the Iranian flight, which later landed, brought Revolutionary Guard advisers, who joined other advisers from the Guard — and Iran’s Lebanese ally, Hezbollah — already based in Yemen.

Iranian advisers assumed a larger role in the offensive

In early August, the Houthis resumed attacks on government forces, focusing on the city of Taiz, in the mountains overlooking the coast, and firing missiles and drones at Mokha.

The Houthi official said Iranian advisers had previously focused on strategic planning and were not in the field. But in the latest escalation, they were “present at all levels,” he said, including planning tactical manoeuvres and working with front-line commanders.

The two regional officials, who are regularly briefed on the latest developments in Yemen, also said Iran provided direct support that helped the rapid advance.

Alsaloum said that in addition to helping in a command role, the Iranian advisers analysed communications and satellite intelligence, capacities the Houthis were lacking.

Iran’s UN mission did not respond to requests for comment.

Pro-government forces were divided

The National Resistance, with some 30,000 fighters, was the strongest pro-government force along the coast. But it had not been involved in major fighting since 2017.

For a month, Houthi forces bombarded its positions with 130 ballistic missiles and 145 suicide drones, according to a National Resistance spokesman, Maj. Gen. Sadiq Dwaid. He said its fighters were stretched over 170 kilometres (100 miles), from Mokha into the mountainous interior, against what he estimated were 75,000 Houthi fighters.

In early September, the Giants Brigade, another militia, came to its aid, helping it to temporarily push back the rebels. But the Giants Brigade had not coordinated with the National Resistance, angering its field commanders, one government official said.

The two forces had a long-standing rivalry rooted in the past struggle between Saudi Arabia and the United Arab Emirates over control of the anti-Houthi movement. That struggle led to the UAE abruptly pulling out of Yemen in January.

There was no “unified command,” said the senior military official. “This was a priceless opportunity for the Houthis.”

A swift advance led to a panicked retreat

On September 9, the Houthis advanced south toward Mokha through a narrow mountain valley, heavily bombarding their opponents.

Having breached their communications, the Houthis were able to listen in and exploit divisions, one of the government officials said, adding that National Resistance leaders lost contact with several field commanders.

By the afternoon, the Houthis had seized the mountain road and a nearby military base, cutting off government supply lines to Mokha. Lt. Gen. Tariq Saleh, the leader of the National Resistance, was forced to flee and then took refuge in Saudi Arabia.

At around 6 p.m. that night, orders went out to National Resistance field units to retreat back to Mokha. When thousands of fighters began arriving, the forces stationed in the port city thought a major Houthi attack was imminent and began to flee, two National Resistance fighters told the AP.

A Mokha resident, Issa Gubwani, said he saw fighters in military vehicles and pickups streaming out of the city. “They left us to face our fate,” he said. Tens of thousands of residents joined the exodus.

The Houthi official said that when the rebels rolled in early on September 10, “the city was empty.”

Government forces are trying to regroup

The senior government military official said Yemeni forces were stunned that Saudi warplanes didn’t strike the Houthis as they advanced on Mokha. The Saudi government media office did not respond when asked for comment.

The Houthis seized weapons and military equipment, including armoured vehicles, rockets, artillery shells and ammunition, most of it from the UAE and Saudi Arabia, two government officials said. The rebels displayed some of the captured weapons in a televised parade.

The National Resistance said it lost 500 fighters in the battles; that could not be independently confirmed. The Houthis have not announced their losses.

As government forces work to regroup, supporters of the various militias have been trading blame and accusations of treason online. The Houthis are meanwhile building defences around the newly captured territories, according to the Houthi official.

“Losing the West Coast is not the end of the battle; rather, it marks the beginning of a fiercer battle,” Brig. Gen. Walid Ziyad, a senior National Resistance commander, declared on social media.

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With a floundering economy and growing restrictions on personal freedoms, 10 years of Houthi rule has left its mark on Yemen’s ancient capital, Sanaa, where some quietly long for how things once were.

The Houthis, a radical political-military group from Yemen’s northern mountains, have imposed strict rule over the large swathe of Yemen under their control, covering two-thirds of the population.

Since the Iran-backed rebels took power in Sanaa in 2014, after long-running protests against the government, the country has gone “back 50 years”, sighed Yahya, 39, who like many prefers not to share his full name for fear of reprisals.

“Before, we thought about how to buy a car or a house. Now we think about how to feed ourselves,” added Abu Jawad, 45.

Already the poorest country in the Arabian Peninsula, Yemen has been devastated by war since 2015, when a Saudi-led coalition launched a failed campaign to dislodge the Houthis.

Hundreds of thousands of people have died through fighting or indirect causes like hunger and disease, with much of the infrastructure in ruins.

Yemen, mired in one of the world’s worst humanitarian crises, remains divided between the Houthis and the government, now based in the port city of Aden.

The Houthis, who adhere to the Zaidi branch of Shiite Islam and claim divine right to rule, have tightened their control over many aspects of daily life.

‘Men, women could sit together’

Sanaa, despite its conservatism, once had “political parties, active civic organisations, NGOs… coffee shops where males and females can sit together”, said researcher Maysaa Shuja al-Deen, of the Sanaa Center for Strategic Studies.

“Now the social and political atmosphere has become very closed,” she added.

Men and women are segregated in public, and Houthi slogans like “Death to America!” and “Death to Israel!” are plastered everywhere, alongside photos of Houthi leaders, Deen said.

Since 2015, Amnesty International has documented numerous cases of activists, journalists and political opponents who were convicted on “trumped-up” espionage charges.

A wave of arrests in June targeted aid workers, including 13 United Nations staff who are still detained.

Majed, the director of a Yemeni non-governmental organisation, said he fled Sanaa for Aden before taking refuge with friends in Jordan, leaving behind his wife and three children.

“I made the decision without thinking too much. Leaving was a risky choice, but it was the only one,” the 45-year-old said from Amman, where he hopes to find a job.

According to Deen, a Yemeni who is also based outside the country, it is now difficult to go against the ruling authorities, or even fail to show support.

“At the very beginning, being silent was an option. Now it’s not even an option,” she said.

“You have to show that you are loyal to the Houthi ideology.”

The Houthis are adept at using social and traditional media, such as their Al-Masirah TV station, to spread propaganda, and have even revised school textbooks and changed the calendar.

The traditional holiday of September 26, which celebrated the 1962 revolution against the former imam, has been moved to September 21, the day the Houthis took power.

Some Yemenis chafe at the change. “Even if they forbid us from celebrating officially, we will celebrate it in our hearts,” said Abu Ahmed, 53, a Sanaa resident.

‘I dream of getting my life back’

However, support for the Houthis’ attacks since November against Israel and ships in the Red Sea, in solidarity with Palestinians during the Israel-Hamas war, seems to be unanimous.

“The Yemenis have always been pro-Palestinian,” said author and Yemen specialist Helen Lackner, highlighting the hundreds of thousands of people who join the Huthis’ weekly demonstrations in Sanaa.

Despite their popularity among ordinary people, the maritime attacks have halted negotiations conducted between the rebels and Saudi Arabia to end the war.

Rim, 43, who has lived with her family in neighbouring Saudi for nine years, has not been able to return to Sanaa to bury her father, or attend the weddings of her brothers and sisters.

“I dream of getting my life back,” said the 43-year-old. In the meantime, she is content to talk to her children about her country.

“I don’t want them to forget that they are Yemeni.”