President Donald Trump cast the United States assault on a Syrian air base as vital to deter future use of poison gas and called on other nations to join in seeking “to end the slaughter and bloodshed in Syria.”

The U.S. blasted the air base Thursday night with a barrage of cruise missiles in fiery retaliation for this week’s gruesome chemical weapons attack against civilians.

It was the first direct American assault on the Syrian government and Trump’s most dramatic military order since becoming president just over two months ago.

So, what action did the United States take against Syria?

A timeline of the conflict in Syria