The Houthis are homegrown. Their name comes from the Houthi family, who launched a religious revival in northern Yemen. In the 1990s, when Salafists began preaching the Saudi brand of Wahhabi Islam on what was essentially Houthi turf, the head of the family, Hussein al-Houthi, led a movement to reaffirm Zaidi Shiite traditions that had guided Yemeni culture for centuries.

Yemen’s central government saw Houthi’s growing influence as a security threat. Under the leadership of then-President Ali Abdullah Saleh, Yemeni armed forces launched a series of wars to beat back the Houthis. In 2009, Saudi Arabia sent its own troops to join in the fight to subdue the Houthis.

By 2011, as populist fervor was coursing through the Arab world, the Houthis had joined with other anti-government groups in Yemen to hasten the downfall of President Saleh. They argued that his leadership had become corrupt, and they called for his ouster.

In 2012, Saleh was forced to transfer executive power to his vice president, Abdo Monsuer Hadi. The same year, the Houthis came to the negotiating table to help draft a power-sharing agreement with other Yemeni factions through a UN-sponsored National Dialogue Conference.

But the NDC came up with recommendations that would have provided the Houthis with less than complete control of their historic lands in the north.

The Houthis were having none of that, and in a political move that continues to confuse observers, they formed a political alliance with their longtime nemesis, the deposed Saleh, who was already seeking to regain power in 2013.

Reporter Iona Craig, who was then living in Sanaa, recalls that the Houthis, with Saleh’s formidable political and military connections, were able in 2014 to gain control of northern Yemeni cities including the capital, Sanaa. “Certainly at the beginning of this war it was Saleh who was really the driving force behind the Houthis and, yes, they were politically aligned to Iran but there was very little evidence, really, of the Iranians supporting the Houthis.”

There was no need for Iranian weapons in 2014. Saleh may have been out of office, but he still controlled much of the well-stocked, American-supplied Yemeni arsenal.

By March 2015, the Houthi/Saleh forces had conquered most of Yemen’s major cities and driven out the caretaker government of President Hadi, thoroughly alarming the Saudi government that supported him.

On March 26, 2015, Saudi Arabia led a bombing campaign to take out the Houthi military and its weapons. The Saudis also instituted a naval blockade aimed at preventing Iranian weapons from entering Yemen. Both the air and sea operations continue as of this writing.

And while claims of Iranian weapons deliveries were seen to be groundless in the opening months of the Yemen war, there is evidence now that the Iranians are assisting the Houthis militarily.

“In the last few months — as you know we’re going into the third year of war now in Yemen — there has been growing evidence of Iranian involvement on the weapons front,” says reporter Craig. “Ballistic missiles … have clearly been modified, and new missiles have been built in Yemen to fire over the Saudi border — long-range missiles that did not exist in the Yemeni arsenal before this war have been used.”

If Iran’s influence in Yemen was hard to detect before, it is unmistakeable now. In the first months of 2017, the Houthis — and Tehran — have boasted of a newfound ability to attack Saudi Arabia. And as the war drags on, Iranian influence may grow.

“This is the risk and this is the danger,” says Craig. “The longer this war goes on, the likelihood is of more Iranian involvement rather than less.” That, says Craig, could drive Washington to step up its already significant material and logistical support of the Saudi-led military coalition.

And, Craig adds, it might even inspire the US to assume a more active role in Yemen. “The Trump Administration [could start] their own proxy war with Iran by bombing the Houthis,” she says, “and that’s the real danger now.”