Attacks on Saudi Arabia's petroleum facilities last weekend knocked out more than half the country's oil output. Houthi rebels claimed responsibility for the assault, although the United States charged that Iran was behind the incident. The attacks are a reminder of the centrality of Saudi Arabia to global energy production and the potential for disruption that results from that role. It also underscores how Riyadh's foreign policy has effects well beyond the Persian Gulf.

Houthi rebels, supported by Iran, have been fighting for control of Yemen since 2014. After the insurgents took control of the country, Saudi Arabia joined with the United Arab Emirates in 2015 to forge a military coalition to restore the former government to power. The result has been a bloody struggle that is considered to be one of the world's worst humanitarian disasters, claiming nearly 100,000 lives in a savage fight.

A cease-fire was brokered last year but it has proven ineffective. The Houthis have turned their focus to Saudi Arabia, attacking pipelines and other parts of its oil infrastructure, along with ships in the Gulf of Hormuz. In August, the rebels used drones to attack an oil field near the Saudi border with the UAE; it had limited effect. Last week's attack on the Abqaiq facilities by numerous drones demonstrates both shrewd targeting and increasing capability, as the facilities are more than 800 km from Houthi-controlled areas of Yemen.