An elite Israel Defense Forces unit conducted a highly unusual raid in Syria earlier this week and destroyed an underground precision missile factory that Israel and the U.S. claim was built by Iran, according to three sources briefed on the operation.

Why it matters: Israeli airstrikes on Syria have increased since the Oct. 7 Hamas attack on Israel as cross-border conflicts between Hezbollah and Israel intensified. But the raid on Sunday was the first ground operation the IDF has conducted in recent years against Iranian targets in Syria.

• The destruction of the factory appears to be a significant blow to an effort byIran and Hezbollah to produce precision medium-range missiles on Syrian soil.
• The Israeli government has stayed unusually silent about it and didn’t claim responsibility in order not to provoke a retaliation by Syria, Iran or Hezbollah, sourcessaid.
• Spokespersons for the IDF, Israel’s Ministry of Defense and the Prime Minister’s Office declined to comment.

Driving the news: Syrian state media and Syria’s opposition organization reported heavy airstrikes by the Israeli Air Force on Sunday night local time in several areas of western Syria, including near the city of Masyaf, which is close to the border with Lebanon.

• State media said at least 16 people were killed and 40 others were injured, and condemned the airstrikes as “blatant aggression.” The Iranian foreign ministry also condemned the attack, calling it “criminal.”
• On Wednesday, a Syrian opposition television channel and Greek Middle East expert Eva J. Koulouriotis bothreported the airstrikes were a cover for an Israeli ground operation in Masyaf.
• Three sources with knowledge of the operation confirmed to Axios that the Israeli Air Force elite unit Shaldag conducted a raid and destroyed the facility.

Zoom in: Two sources said Israel briefed the Biden administration in advance of the sensitive operation and the U.S. didn’t oppose it. The White House didn’t respond to a request for comment.

• The Israeli special unit surprised the Syrian guards at the facility and killed several of them during the raid, but no Iranians or Hezbollah militants were hurt, one source said.
• The special forces used explosives they brought with them in order to blow up the underground facility, including sophisticated machinery, from inside, two sources said.
• The airstrikes were intended to prevent the Syrian military from sending reinforcements to the area, one source said.

Behind the scenes: Two sources with direct knowledge told Axios the Iranians began building the underground facility in coordination with Hezbollah and Syria in 2018 after a series of Israeli airstrikes destroyed most of the Iranian missile production infrastructure in Syria.

• According to the sources, the Iranians decided to build an underground factory deep inside a mountain in Masyaf because it would be impenetrable to Israeli air strikes.
• The sources claimedthe Iranian plan was to produce the precision missiles in this protected facility near the border with Lebanon so that the delivery process to Hezbollah in Lebanon could take place quickly and with less risk of Israeli airstrikes.
• Israeli intelligence services discovered the building process and monitored it for more than five years under the code name “Deep Layer”. The Israelis realized they would not be able to destroy the facility with an airstrike and would need a ground operation, one of the sources said.
• The Israeli military considered conducting the operation at least twice in recent years but it wasn’t approved because of the high risk, one source said.

Editor’s note: This story was corrected to show that the Israeli Air Force elite unit Shaldag conducted the raid, not the IDF unit Sayeret Matkal.