King Khalid International Airport in Saudi Arabia was attacked several times between October 8 and October 11 by drone and missile strikes believed to have been launched by Houthi forces. On October 8, two attacks struck airport facilities and a Saudia aircraft, killing three Saudi citizens, including an airline pilot, and injuring a number of other people. The violence escalated dramatically on October 10, when a missile struck the airport and killed 12 people while injuring more than 300.

One of the wounded later died, raising the death toll from that strike to 13. Victims included Saudi citizens as well as foreign nationals from several countries, underscoring the international consequences of attacking one of the Middle East’s major transportation hubs.

A series of increasingly lethal Houthi missile and drone attacks on Saudi Arabia, culminating in repeated strikes on Riyadh’s King Khalid International Airport, has demonstrated that the Yemen-based movement remains capable of threatening targets deep inside the kingdom despite Saudi Arabia’s sophisticated military defenses. The last time Saudi Arabia faced attacks from conventional weapons was in the early 1990s from the regime of Saddam Hussein, making this a type of threat most Saudi civilians aren’t used to confronting.

The attacks underscored the evolving security threats facing Saudi Arabia. The kingdom possesses Patriot, THAAD and other sophisticated air-defense systems, and Saudi forces intercept many incoming projectiles. But no defensive system can stop 100% of incoming attacks. Repeated waves of ballistic missiles, cruise missiles, and relatively inexpensive drones can strain radar coverage and consume costly interceptor missiles. Reports also indicate that Saudi and allied interceptor inventories have come under pressure during the wider regional conflict.

The immediate cause of the escalation is the renewed Saudi-Houthi war in Yemen. Saudi Arabia has again been conducting airstrikes while supporting Yemeni government forces attempting to push the Houthis back from strategically important territory near the Red Sea and Bab al-Mandab. The Houthis appear to be responding by attacking economically and politically sensitive Saudi targets such as airports, energy installations, and potentially transportation infrastructure rather than limiting the conflict to Yemen.

King Khalid International Airport was struck again on October 11. Saudi authorities said a projectile hit Terminal 4, starting a fire, killing a Pakistani resident and injuring 11 others. King Khalid Airport has consequently remained closed while authorities conduct damage assessments and safety inspections, disrupting airline operations and forcing flights to be cancelled or diverted.

But the Houthi campaign extends beyond Riyadh. Saudi authorities have reported a projectile near King Fahd International Airport in Dammam, while Saudi defenses intercepted a cruise missile near Riyadh and a drone over the Eastern Province. The Houthis have also threatened Saudi oil facilities and warned airlines against operating through much of Saudi airspace.

While the Houthis are unlikely to defeat Saudi Arabia militarily or occupy significant Saudi territory, they have demonstrated that they can periodically penetrate Saudi defenses and inflict casualties hundreds of miles from Yemen. That gives them the ability to disrupt aviation, threaten oil infrastructure, frighten investors, and impose substantial economic costs on Saudi Arabia.

The growing Houthi attacks on Saudi Arabia could renew a large-scale conflict between Saudi Arabia and Yemen. That could disrupt global shipping through the Red Sea and energy supplies from Saudi Arabia to world markets. Since Iran has long provided the Houthi with weapons, cash, and training, the possibility that Saudi Arabia could attack Iran directly in retaliation is increasing, and such a move could trigger a much larger conflict in the Middle East.