Syria's conflict is the most violent to emerge from last year's Arab Spring, taking thousands of lives over the past 18 months.
After dictatorships fell in Tunisia, Egypt, Libya and Yemen, Syrian President Bashar Assad's government resorted to a brutal crackdown and mass killings to stay in power.
The United States has called for him to step down and has imposed economic sanctions. There is disagreement over what other steps the U.S. should take.
Assad long has helped Iran aid Hamas and Hezbollah, destabilizing Lebanon while threatening Israel's security and U.S. interests in the Middle East.
But extremists among the Syrian opposition, Assad's weapons of mass destruction and worries about Israel's border security have policymakers wary about deeper U.S. involvement.
- Winners and losers under Obama's immigration...
- Fact check: Obama's claims on illegal...
- Investigators may have recovered up to 30,000...
- Ice snarls Michigan roadways, airport runways
- 37 homes collapse, dozens injured in...
- Consumer group lists '10 worst toys' for kids
- Q&A with President Henry B. Eyring, Elder L....
- Obama immigration plan good, not great for...
- President Obama's immigration reforms... 63
- Utah members of Congress slam Obama's... 55
- Obama to announce immigration action... 30
- Pastors opposed to same-sex marriage... 28
- Q&A with President Henry B. Eyring,... 22
- Fact check: Obama's claims on illegal... 18
- President Obama's immigration speech... 14
- Boehner: 'We will not stand idle' on... 14