Iran looms large in the debate over how to respond to the August 21 chemical weapons attack in Syria that killed hundreds of civilians. For proponents of a muscular American response, strikes would be as much about deterring Iran as about punishing the regime of Syrian President Bashar al-Assad. “A failure to stand against the use of chemical weapons,” U.S. President Barack Obama maintained in his address to the country on Tuesday, “would weaken prohibitions against other weapons of mass destruction and embolden Assad’s ally, Iran, which must decide whether to ignore international law by building a nuclear weapon or to take a more peaceful path.” Meanwhile, National Security Adviser Susan Rice and Secretary of State John Kerry have both increasingly focused on Iran in their public advocacy for a U.S. strike.

