Anonymous Israeli sources shared with Reuters some details of how last night’s operation unfolded.

One of the agency’s interlocutors said that Mossad commandos covertly placed weapons, including explosive drones, on Iranian territory. These were used to attack a surface-to-surface missile base near Tehran.

They also used precision-guided weapons to strike air defense systems at the start of the air raids, which reduced the threat to Israeli aircraft. Mossad released grainy black and white footage in which two camouflaged figures can be seen in a desert-like landscape.

The decision to launch the operation, planned over many months, on Friday was made on Monday, following a phone call between Prime Minister Benjamin Netanyahu and U.S. President Donald Trump. Meanwhile, Israel sought to give the impression that it was banking on the success of U.S.-led negotiations on Iran’s nuclear program.

Reuters notes that this deception may have worked: just before the Israeli strikes, Iranian officials dismissed the likelihood of an imminent attack and viewed signs of preparation as psychological pressure.

One of the agency’s five sources (this one in the Israeli military) noted that Israel did succeed in achieving the element of surprise at the start of the operation. However, the operation is not over, and “difficult days lie ahead.”