Nearly a decade ago, after a string of assassinations of Iranian nuclear scientists shook Tehran, Iran’s Islamic Revolutionary Guard Corps was assigned the task of guarding them. The very presence of the powerful IRGC was meant to be deterrent enough to prevent enemy intelligence operatives from further killings, conducted as part of a covert war waged in earnest at the time by Israel and the United States to slow down Iran’s nuclear advances.

“Israel targeted the nuclear scientists because it understood that they did not have the security protection of the IRGC,” said Gen. Mohammad Hassan Kazemi, the deputy commander of the IRGC security branch. But any claim such a deterrent effect still existed disappeared Nov. 27, when the brazen killing in broad daylight of Mohsen Fakhrizadeh – long reputed to be the “father” of Iran’s nuclear program – exposed deep vulnerabilities in Iran’s security and intelligence apparatus.

Though close to retirement and using a cover story as an academic – which was used to deny inspectors of the International Atomic Energy Agency (IAEA) access to him, despite repeated requests – Mr. Fakhrizadeh in fact held the rank of deputy defense minister and was given a dayslong state funeral. He was a known target, and would have been well protected by the IRGC’s Ansar-ol-Mahdi “secret service” unit. 

“The Fakhrizadeh assassination came as a shock, not because they didn’t expect it, but exactly because they did expect and prepare for it, and yet they couldn’t prevent it,” says Maysam Behravesh, an intelligence analyst on contract with Iran’s Ministry of Intelligence and Security from 2008 to 2010. “This and past hostile operations could not have been carried out successfully, against all odds, had there not been a complex network of spies and moles deep in Iran’s security structure and intelligence community,” says Mr. Behravesh. Iran blames Israel’s Mossad intelligence agency, which has a decades long history of conducting targeted assassinations across the Middle East and beyond. Israel has not denied a role, nor sought to dispel the sense that it operates with impunity in the Islamic Republic.