A Shiite Crescent running from Iran through Syria and to the Mediterranean would be bad for Sunni powers and Western democracies.
The U.S. shoots down a Syrian fighter-bomber. Iran launches missiles into eastern Syria. Russia threatens to attack coalition aircraft west of the Euphrates. What is going on? It might appear a mindless mess, but the outlines are clear.
The great Muslim civil war, centered in Syria, is approaching its post–Islamic State phase. It’s the end of the beginning. The parties are maneuvering to shape what comes next.