An Iranian nuclear scientist was killed Jan. 12 in an IED explosion in the Iranian capital. According to the early details, Massoud Ali-Mohammadi was killed around 7:30 a.m. local time near his home in northern Tehran's upscale district of Qeyterieh with a bomb that some report was hidden in a trashcan and others state was part of a booby-trapped motorcycle. Authorities in Tehran identified Ali-Mohammadi as a professor of nuclear physics at Tehran University. There are reports he may have been affiliated with the country’s controversial nuclear program, but his exact importance with respect to the nuclear program remains unclear. This is also not the first time that an Iranian nuclear scientist has been killed in mysterious circumstances. Three years ago, a noted Iranian nuclear scientist, Ardeshir Hassanpour, was killed. At the time, STRATFOR had learned that the Israeli intelligence service Mossad was behind the assassination. Indeed, even this time around, Iranian officials have pointed fingers at the Jewish state. It is, however, too early to tell if that is the case. Assassinations of individual scientists and even defection or kidnapping of others are not unprecedented. Furthermore, there have been bombings in recent months that have targeted senior military commanders of the country’s elite military force, the Islamic Revolutionary Guard Corps. The timing of this attack (the first involving the use of an IED against a nuclear scientist), however, comes at a time of considerable domestic unrest and increasing international pressure on Iran to accept an enrichment compromise or face potential military action on the part of the United States or Israel. Today’s attack will provide the pretext for Iranian authorities to crack down even harder on opponents at home who are already accused of collaborating with foreign enemies of the state. More importantly, it will make Tehran even more intransigent on the nuclear issue as the Islamic republic cannot be seen as caving into pressure, especially not from the West and Israel. The killing of the scientist also places considerable pressure on Iran to engage in retaliatory action.