America should have hit Assad four years ago

The better approach following Assad’s chemical attacks in 2013 would have been to launch both punitive and preventive strikes against his military, trying to eliminate as many as possible of the aircraft that could be used to deliver chemical weapons, followed by the imposition of a no-fly zone to keep the remainder of his air force grounded, and a threat to strike again should he use ground-based weapons to launch chemical strikes in the future. This is more than what was likely in the offing, but would have been militarily feasible. Stand-off weapons such as cruise missiles could have destroyed a significant number of Syria’s fighter jets and helicopters on airfields with no risk to American service members and little risk of civilian casualties (since military hangars and runways are not close to residential buildings).

As for a no-fly zone, the U.S. military enforced one against the Saddam Hussein regime in northern Iraq for over a decade with spectacular humanitarian benefits; in Syria, regime planes flying over most of the country’s cities would have been in range of American aircraft patrolling even outside Syrian airspace. This is what Assad feared the U.S. would do after that first massive sarin attack; while the administration was considering strikes, he essentially stopped his military operations throughout the country. Had the administration gone forward, it still could have pursued a disarmament deal (since Assad would have been desperate to get us to stop our strikes), while launching a broader diplomatic push to diminish the violence in Syria.