That would be an easier discussion for the Russians, who began conducting airstrikes Wednesday, than the Americans, who've been bombing Syria for more than a year.

For Russian President Vladimir Putin and his generals, the definition of "terrorist," when it comes to the increasingly turbulent Syrian civil war, is simple: anyone who uses violence to try to topple President Bashar Assad.

Assad is a dictator, but he's Moscow's dictator. Just as the late Iraqi strongman Saddam Hussein was Washington's dictator, for decades, before President George W. Bush turned against him and launched an ill-fated March 2003 invasion whose consequences are still playing out more than a dozen years later across the Middle East, from Syria and Iraq to Libya and Iran.

For President Barack Obama and his top military aides, it's becoming more complicated by the day to say just who is a terrorist in Syria.