After months of relatively minimal involvement in the U.S.-Iran war, the Iran-backed Houthi militant group in Yemen is making a delayed but consequential entrance that threatens to reignite their decade-old conflict with Saudi Arabia, an American ally.

Over the past days, the Houthis claim to have launched missile and drone strikes on oil tankers in the Red Sea after they declared a naval blockade on shipping linked to Saudi Arabia. A Saudi military coalition has launched airstrikes in Yemen, and the Houthis say that they have fired missiles and drones at the kingdom.

The Houthis have long portrayed themselves as key members of what Iran calls “the axis of resistance.” But while the Houthis are close to Tehran, analysts say that they are also a distinctly Yemeni faction, with their own particular motivations that have pushed them to escalate at this moment.

Here’s what to know about the Houthis and their relationship with Iran.

Who are the Houthis?

The Houthis are Shiite militants who have been fighting Yemen’s internationally recognized government for about two decades. They overran the Yemeni capital, Sanaa, in 2014, forcing the government to flee to the southern city of Aden.

The following year, a Saudi-led coalition launched a bombing campaign to oust the militants, but those efforts failed, leaving the Houthis in power in northern Yemen. Hundreds of thousands of people have died from the violence, famine and disease that ensued, exacerbating one of the world’s worst humanitarian crises.

The Houthis oppose Israel and the United States. They are part of a group of Iran-backed forces across the Middle East, along with Hamas in Gaza, Hezbollah in Lebanon and armed militia in Iraq.

The United Nations helped broker a cease-fire between the Houthis and Saudi Arabia in 2022. But since then, negotiations toward a long-term peace agreement have stalled, leaving Yemen in a fragile stalemate.

The Houthis had continued to launch attacks on their adversaries in the region, but had avoided attacking Saudi Arabia until this month.

During the two-year war in Gaza that began in late 2023, the Houthis disrupted international shipping by firing on Israel and at passing vessels in the Red Sea in what they described as a campaign on behalf of the Palestinians.

Crucial to the Houthis’ power is the Bab al-Mandab Strait, a narrow waterway off Yemen’s southwestern tip. The strait connects the Red Sea to the Gulf of Aden and is one of the world’s most important shipping routes.

Have the Houthis been involved in the war?

Until recently, the Houthis’ involvement in the broader Iran war had been cautious. Some experts said that the group had been weakened by a weekslong bombardment by the United States and Israel last year and that it had been forced into a careful calculation about how much of a dwindling arsenal it could afford to spend.

The new front in the war started to open earlier this month, when the Houthi authorities accused Saudi Arabia of attacking Yemen’s main international airport, in Sanaa, in a dispute over an Iranian plane that tried to land there.

Analysts say that Iran has most likely urged the Houthis to disrupt shipping in the Red Sea, choosing a moment when both Tehran and the Yemeni group could benefit from such an escalation.

With the Strait of Hormuz effectively closed for months, the Red Sea has become a vital alternative route for the transportation of Saudi oil and gas.

For Iran, Houthi attacks on Saudi oil tankers offer an effective way to further disrupt global energy markets and pressure President Trump, analysts say. For the Houthis, the attacks offer a way to pressure Saudi Arabia, giving the group leverage as it demands monetary and political concessions from the kingdom.

What is the Houthi relationship with Iran?

The Houthis are neither a direct conduit for Iranian interests in Yemen nor fully independent of Tehran’s influence.

Analysts have said that Iranian support helped the Houthis evolve from a group of poorly organized rebels to a powerful armed presence in the region with an arsenal of cruise and ballistic missiles and long-range drones.

But the Houthis have always weighed loyalty to Tehran alongside domestic calculations. The group has used the alliance with Iran to gain power and fend off rival forces, turning the militia into a de facto government in northern Yemen. During the past few years, the Houthis have begun to speak about themselves as the legitimate government of Yemen, dismissing the internationally recognized Yemeni government as a weak Saudi proxy.

In recent statements, Iranian officials have referred to the Houthis in similar terms, indicating at least tacit support for the Houthis’ bid to become a national and regional power.

Vivian Nereim contributed reporting from Riyadh, Saudi Arabia.