Sources familiar with the details told the Wall Street Journal that for months Israel smuggled explosive drone parts into Iran. They were smuggled in suitcases, trucks and tankers, along with additional ammunition. The Mossad smuggled the drones through commercial channels, and agents on the ground collected and distributed them to teams that took part in the attack. Israel trained the leaders of these teams in a third country, who then trained the teams in the field. At the beginning of the attack, teams with drones positioned themselves near Iran's air defense systems and close to missile launch sites. When the Israeli attack began, some teams disabled the defense systems, while other teams attacked the missile launchers. According to sources, this explains Iran's limited response to the initial attack.