For four decades, the U.S. and Iran have been locked into what is essentially an ongoing, low-grade war. Since its inception in 1979, the Shiite theocracy, now run by Supreme Leader Ayatollah Ali Khamenei and a council of top clerics, has considered the U.S. the “Great Satan” — an intruder in the Middle East and a primary obstacle to the mullahs’ goal of sustaining and spreading their Shiite Islamic revolution.