Saudi Arabia fared far better on Sunday, when it escaped missile and drone attacks on its oil heartland with no serious damage, than 18 months ago when strikes forced it to temporarily shut its industry down.
Military experts say that is partly down to better preparation. But the kingdom still remains more vulnerable to drones and low-flying cruise missiles than to high-flying ballistic missiles it was able to shoot down this week.
A Sept. 2019 strike hit two key plants with cruise missile and drones. This time, Riyadh said it foiled the attack, with no property loss.
Yemen's Iran-aligned Houthi movement, which is battling a Saudi-led coalition, claimed responsibility for Sunday's strike at an oil storage yard at Ras Tanura, site of a refinery and the world's biggest offshore oil loading facility, and a residential compound in Dhahran used by oil giant Saudi Aramco.
The two sites in the Eastern Province are located just a few km from the Aramco facilities targeted in 2019. Riyadh blamed that attack on Iran, a charge Tehran denies.
"It looks like the Saudis have been working hard to fill in the gaps, including with the Patriot deployment at Ras Tanura, which now appears to have paid off," said Jeremy Binnie, Middle East and Africa Editor of Janes Defence Weekly, referring to a U.S.-made long-range surface-to-air missile system.
Binnie said U.S. military reinforcements at Prince Sultan Air Base after the 2019 attacks had helped free Saudi assets to be moved elsewhere, and France and Britain had also provided radars to help track low-flying threats such as drones.
The Patriot system is designed mainly for high-altitude ballistic missile attacks, which the kingdom has often had to deal with since intervening at the head of a coalition in Yemen six years ago.
But Saudi Arabia remains vulnerable due to its size, evolving threats and human error, the experts said.
Low-flying cruise missiles and drones, which are much smaller targets, may not be picked up in time by ground-based radar. Intercepting drones with Patriots is also extremely expensive, with each missile costing around $3 million.
"The Saudis are not badly equipped," said Douglas Barrie, senior fellow for military aerospace at London-based IISS think tank.
"There are a range of things to use against UAVs and ballistic missiles," he said, using an acronym for unmanned aerial vehicles, or drones. "They have used them successfully and they are getting better at it, but you are never, ever going to be 100% successful."
The Houthis said on Sunday they had launched a Zulfiqar missile, which has a range of some 700 km, and ten armed drones at the eastern cities of Ras Tanura and Dammam. They fired seven Badr missiles and four drones at the southern cities of Asir and Jazan, their military spokesman said.
The movement recently stepped up cross-border attacks in a conflict widely seen as a proxy war between Saudi Arabia and Iran, locked in a decades-old rivalry for regional influence.
While the attacks did not result in any oil production outages, they underscored "just how dangerous the security environment remains in the region nearly 18 months after the September 14, 2019" strikes, said Helima Croft, head of global commodity strategy at RBC Capital Markets, in a research note.
Saudi Defence Ministry spokesman Colonel Turki al-Malki said on Al Arabiya television channel on Monday that the kingdom was capable of protecting its economic facilities.
"Saudi Arabia has a great deterrent force against any threat, regardless of its source," he said.