Here are a few things we do know about the Houthis' firepower.

“The Houthis kind of have three named missiles, or rocket families, that they refer to a lot," said Arterbury. "We witness the Burkan — that was the one you know they fired at Riyadh; they’ve actually fired several of those into Saudi [Arabia], but more famously it’s gotten a lot more attention; then the Qaher-class is a shorter-range one that they tend to fire across either the Saudi border, or they’ll fire at kind of hot front lines within Yemen. And finally, you have a third class called the Zelzal, which means 'earthquake' both in Farsi and Arabic, and those are actually — the Zelsal-1 and -2 are actually probably more like improvised rocket-assisted mortars like you witness some groups using in Syria. The Zelzal-3 is a bit more unclear; it might be closer to a short-range ballistic missile, but the Qaher is kind of their go-to medium-range.”

On the other side of this missile war is one of the its more puzzling facts, said Aaron Stein of the Atlantic Council. “The Saudis should be slightly better at finding these things,” he said, particularly of the Houthis' longer-range, Iranian-made Qiom rockets, “because there are similar launch points that we’ve seen. And there are Patriot units on the border; Patriot has 180-degree field of fire in the engagement zone. So because it has 180-ish degree field of fire, you need two for 360.

“But in this case you’re only oriented towards a border, you should be able to point it more or less at Sa’dah so your radars will pick it up earlier and you can get a good weapons track on it. Or at least try and shoot it down closer to the border,” he said. “You have to be asking yourself why the Saudis aren’t pointing their damn Patriots in the right position?”

Not that Scud hunting, as Stein puts it, is an easy task, broadly speaking. “In fairness to the Saudis, to be nice to them, road-mobile Scuds are very, very hard to hit. And the Qiom is, at its core, a road-mobile Scud. Even the best of the best — the U.S., the Israelis — have trouble Scud hunt[ing] because, you know, deserts are big, Scuds are small, and you have to patrol a lot of territory to find these things…But they keep firing from around the same area.”

The U.S. and the Saudis allege many of the Burkans are actually Iranian Qiom missiles (customized -B and -C Scuds) that have been disassembled, shipped over water, then driven in trucks to a storage point for re-assembly. Many routes taken, according to the Chatham House, have run through Oman and into Yemen’s more sparsely populated east. It’s a trade that Oxford’s Kendall says has been “extremely lucrative” for Yemen’s shady power brokers.

“The difference I’ve seen over the last two years in my various trips has been stunning,” she said, “from practically traffic jams going over the border from Oman into Yemen to now fresh fruit hanging in the streets, new shops, spanking new hotels opening at $250 a night, new roads being built — it’s incredible. Most ordinary people can’t get anywhere close to that. So it must just be money laundering and fueled by the smuggling industry.”

“There’s obviously no end-use certificates on any of these things,” said Stein of the weapons, like Iranian-made rockets, and how they make it to Houthi hands. “So we have no idea when these missiles were first put in. They could have been put in five years ago for all we know, 10 years ago.”

The bottom line here, said Arterbury, is “the Houthis have kind of a become a low-cost, medium-high reward way of Iran countering Saudi Arabia in the peninsula. And of course, the most dramatic way that you could witness this is through missile tech.”

“The missiles that they’re launching now, judging by the photos released by the [Defense Intelligence Agency] and the Pentagon, are not indigenous to Yemen’s stocks. So it has kind of morphed and metastasized with time,” Arterbury said. “And honestly for Saudi [Arabia], they always saw Iran from the very beginning and they probably overstated it, but now their kind of nightmare has become a reality.”

That reality has come in the form of Burkan-1 short-range ballistic missiles launched at southwestern Saudi cities — Jizan, Najran, Abha, and Al-Tuwai — and almost as many at Saudi coalition forces inside Yemen, mostly in Taiz.

While the Saudis have purchased Patriot PAC-3 anti-missile systems, they don’t appear to be using them. Rather, most of the Saudi intercepts are assumed to use Patriot PAC-2 systems, with a blast-fragmentation warhead like the interceptors the U.S. military deployed in the Gulf War in 1991.

Coalition navies have had their chance to fend off missiles and remote-controlled boat bomb attacks, too. Twice in October 2016, Houthis launched cruise missiles at the American destroyer USS Mason (DDG-87). The Navy responded by launching Tomahawk cruise missiles at the suspected coastal radar stations where the attacks were believed to have originated.