The overnight attack by Houthi forces in Yemen on a Saudi Arabian airport represents a significant escalation in their ongoing war. That's partly because the attack wounded 26 civilians and could have killed many more. But it's also because Iran's hand appears to lurk close here.

First off, there's the tactical nature of the attack itself. Both the Saudi and Houthi authorities say that the missile used was a cruise variant rather than a ballistic missile. But unlike most Houthi missile attacks, which have a sketchy record on accuracy, this missile was stunningly accurate. True, Abha is closer to the Yemeni border than the vast majority of Saudi cities. Still, at more than 80 miles from the Yemeni border, it isn't exactly a layup, especially considering that the target was a specific building. That suggests Iran either supported the Houthis with targeting data from Saudi soil, or with targeting equipment attached to the missile's guidance system, or with the provision of an especially accurate missile.

Moral questions aside, this is an impressive attack that evidences advanced capabilities. Iran's Revolutionary Guard likely provided those capabilities.

There's also the strategic measure of the airport targeting. While the Houthis have repeatedly targeted high-value facilities in Saudi Arabia, they have rarely directly struck a major civilian facility such as an airport. And Abha airport serves as a major transit hub for Saudi tourists. Houthi targeting of the airport would thus have very likely required a prior sign off by Revolutionary Guard liaison officers. The Iranians know that this attack — even if a low-yield warhead was used — might have killed a large number of civilians and thus invite aggressive Saudi retaliation, perhaps against Iran itself. While it is true that the Houthis operate as an ally and occasional subordinate to Iran rather than an ideological subordinate in the vein of the Lebanese Hezbollah, they understand Iranian control on matters involving Saudi soil. It's non-negotiable: The Revoltionary Guard is the means of Houthi missile access.

Ultimately, this incident raises the risk of new escalation in Iranian-Saudi tensions. It also explains why President Trump is right to provide materiel support to the Saudi regime. Absent the quality of American support that those weapons provide, the Saudis would be far less amenable to hearing American calls for restraint and more predisposed to lashing out at what they see as an existential Iranian threat.