Guided by spies and artificial intelligence, the Israeli military unleashed a nighttime fusillade of warplanes and armed drones smuggled into Iran to quickly incapacitate many of its air defenses and missile systems. With greater freedom to fly over Iran, Israel bombarded key nuclear sites and killed top generals and scientists. By the time Iran mustered a response hours later, its ability to retaliate — already weakened by past Israeli strikes — was greatly diminished.

“This attack is the culmination of years of work by the Mossad to target Iran’s nuclear program,” said Sima Shine, the former Mossad research director who is now an analyst at the Institute for National Security Studies.

Israel’s element of surprise was enhanced by Iranian officials’ apparent assumption that Israel wouldn’t attack while talks over its rapidly advancing nuclear program were ongoing with the U.S.