U.S warplanes with two Arab partners hit a dozen targets in Syria, including oil refineries, a major source of revenue for ISIS. The strikes are happening as President Obama spoke to world leaders at the United Nations - making it clear that he's determined to destroy ISIS.
"There can be no reasoning – no negotiation – with this brand of evil," Obama said at the U.N. General Assembly. "The only language understood by killers like this is the language of force."
As the threat of lone wolf attacks at home rises in the wake of these airstrikes.
What are the chances they'll even work?
CNN's Barbara Starr has the latest.