So, here’s the administration’s case for action:

The Weapons

The U.S. says it has known about the Syrian chemical-weapons program for several years because of intelligence efforts. Senior administration officials say it is “old, vast, expansive, very well run, tightly commanded, and tightly controlled.” And while there are many members who operate in the chemical-weapons apparatus, President Bashar al-Assad is the final “decision-maker” with all attacks.

“He’s ultimately in charge of deployment,” a U.S. official said Friday. The “overall use and overall program is firmly under his control.”

The Assad regime has several types of chemicals in its weapons stockpiles, including mustard, sarin, and VX, and it has used these weapons “on a small scale” in the past year on its own people. To the Syrian government, the U.S. says, chemical weapons are just “one of many tools in its arsenal.”