New details have emerged about how Israeli special forces carried out a commando raid in Syria on Sunday that destroyed a Hezbollah missile production facility, according to American and Western officials.

The secret facility in northwestern Syria was hit with airstrikes and stormed by ground forces who rappelled from helicopters to seize evidence in a predawn raid, the officials said.

Syria’s state news agency, SANA, reported on Monday that 18 people were killed and 37 more were injured in the attack, making it one of the most deadly the country has seen in months.

Here is what to know about the attack, Israel’s latest long-range strike in its multiple conflicts against Hezbollah in Lebanon, Hamas and other militant groups in the Gaza Strip and the West Bank, as well as Iranian and Syrian targets. The officials spoke to The New York Times on condition of anonymity to discuss sensitive intelligence.

The raid began with airstrikes, and then commandos moved in.

Israel hit the sprawling facility with airstrikes late Sunday and early Monday, Western officials said, before dropping in commandos to penetrate the facility’s reinforced inner rooms, which were buried deep underground in a mountainside and could not be reached with airstrikes alone.

The decision to involve troops on the ground who were armed with demolition charges was made to ensure that the facility was destroyed entirely, the officials said. Israel had struck the facility repeatedly in the past, and in 2018 it assassinated a Syrian rocket scientist who worked at the center developing precision-guided munitions.