An Iranian group has killed American civilians, allied itself with Saddam Hussein, and holds a spot on the State Department’s terrorist watch list. So why might it become America’s newest friend in the Middle East? Hint: Tehran. In August 2002, intelligence reports revealed secret nuclear facilities in the Iranian cities of Natanz and Arak. The revelation left officials in Tehran speechless, in large part because the evidence was not gathered by the United States or any of its allies. Rather, the courier of such sensitive intelligence was the Mujahedin e-Khalq (MEK), a decades-old Iranian dissident group. In most cases, dissident...