Andreas Krieg, a professor at King’s College London, said this experience in challenging Israel’s cutting-edge air defenses has given the Houthis confidence and expertise as they now strike Saudi Arabia.“They’ve learned how to over-saturate the radars,” he said.The Houthis, working with allied militias in Iraq, have also targeted Saudi oil installations, including a vital pipeline used to export oil through the Red Sea while movement through the Strait of Hormuz is limited. The Houthis have also seized territory in Yemen near the Bab el-Mandeb, a key Red Sea waterway, putting additional pressure on Saudi oil exports.MiscalculationMichael Ratney, a former U.S. ambassador to Saudi Arabia, says the kingdom assumed the Houthis wouldn’t strike civilian targets like airports. Doing so marked “a paradigm shift,” he said.Ratney, now an adviser at the Center for Strategic and International Studies, said the Saudis now find themselves in a position where they have to respond while also trying to prevent the fighting from spinning out of control.“They can’t not strike back — they were attacked in a very brutal way by their archenemies,” he said. “They need to exert military pressure on the Houthis and then find a way to kind of deescalate.”Rather than sending troops into Yemen, the Saudis will likely launch airstrikes against the Houthis and ramp up support of nationalist forces, several analysts said.“It will be surrogate warfare,” Krieg said.A formidable forceWhile the Houthis don’t have the firepower of Saudi Arabia, they have grown into a fearsome force controlling roughly one-third of Yemen thanks to help from Iran.The United Nations estimates that the Houthis by 2024 had recruited up to 350,000 fighters. That’s up from just 30,000 in 2015, when Saudi Arabia intervened in the internationally recognized Yemeni government’s civil war against the Houthis and imposed a naval blockade.Ratney says the Houthis now have a “symbiotic relationship” with Iran and should not be seen as an Iranian puppet.The strikes on Saudi airports and economic assets symbolize a sharing of lessons in asymmetric warfare between the Houthis and the Iranians: how to not just puncture expensive air defenses, but also damage vulnerable energy installations and threaten global maritime routes.Passengers in Bangladesh on Monday after their Saudi Arabia-bound flight was cancelled.Piyas Biswas / SOPA Images via Getty“Over the course of the past few years, the Iranians have been innovating and sharing that with the Houthis and it’s gone both ways. The Houthis have been innovating, and sharing it with the Iranians,” Ratney said. “It’s no coincidence that they’ve ended up with a similar approach.”Their recent military successes have made the Houthis feel “untouchable,” said Farea Al-Muslimi, a fellow at Chatham House focused on Yemen.“It’s very hard to convince a man he’s going on the wrong side if he just moved forward and he has a gun in his hand,” he said. But the Houthis are now likely to suffer a brutal Saudi counterattack, he said.