The Syrian civil war and recent allegations of chemical-weapons can test the wits of foreign policy experts. Here's a look at the latest developments and how Syria and the world got to this point:
THE SYRIAN CONFLICT
Now in its third year, the civil war in a small country with a population of about 23 million is complicated and brutal. There are heavy civilian casualties on both sides.
Rebels, some of them Islamic extremists, fight government loyalists. It's essentially a regional proxy war increasingly fought along sectarian lines, pitting Sunni Muslims against Shiite Muslims and threatening regional stability.
By mid-2011, a loose coalition of rebels and anti-government tribal groups had formed the Free Syrian Army whose goal was to topple President Bashar Assad. Rebels appeared to be gaining the upper hand and they occupied more and more territory. But over the past few months the military has scored a string of victories.
Assad's government increased its pressure on rebels as pro-democracy Arab Spring movements swept through the region last year. The United Nations estimates that roughly 1.5 million people have fled the fighting, many into Lebanon.
THE WORLD'S RESPONSE
Even before the alleged chemical attacks, the Assad government was hit with an increasing number of penalties from European countries and the United States.
While Assad gained increasing support and supplies from Russia and Iran, escalating sanctions by the European Union and the United States put more pressure on people struggling with food and fuel shortages and inflation.
OBAMA'S RED LINE
Last summer, President Barack Obama said that Assad's use of chemical weapons would cross a red line, suggesting greater U.S. intervention. Then in June, the White House said it had conclusive evidence that Assad had used chemical weapons against rebel fighters, and Obama decided to respond by authorizing the arming of Syria's rebels.
It was a turning point for the U.S., which up to that point had avoided getting drawn into the conflict militarily.
A chief U.S. concern had been that U.S.-supplied weapons could fall into the hands of al-Qaida-linked militants fighting alongside the rebels.
THE TIPPING POINT
On Aug. 21, the Obama administration says, Assad's government unleashed a chemical attack outside Damascus. The government of Syria blamed the attacks on rebels.
Estimates of the death toll varied. Activists and those who live in the area have said well over 1,000 people died in the attacks. Secretary of State John Kerry put the toll at 1,429, of whom 426 were children. The nonpartisan humanitarian group Doctors Without Borders has put the death toll at 355.
The Syrian Observatory for Human Rights, one of the main groups monitoring casualties in Syria, said Saturday it has been able to confirm only 502 deaths.
Obama has decided the U.S. should take military action against Syria, and while he has the authority to act alone, he will seek authorization from Congress. Obama is considering what's described as a limited and narrow action.
He made the comments after the U.S. released an intelligence assessment that found with "high confidence" that Assad's government carried out the chemical attack.
But Obama has not yet been able to show that Assad himself ordered the attacks or spelled out how military strikes might deter future use of chemical weapons in the region.
SHORTAGE OF ALLIES
It's been hard for Obama to assemble an international coalition to confront Syria.
That's because burnout over long engagements in Iraq and Afghanistan, and the unpopularity of military adventures in Muslim countries, have wearied traditional Western allies.
Britain, a stalwart ally in the wars in Iraq and Afghanistan, won't play a direct role in any U.S. attack this time. British lawmakers abruptly refused to approve military action.
The only allied leader to openly express willingness to join a U.S. attack on Syria was French President Francois Hollande.
The German government also said it isn't considering joining military action against Syria.
A MATTER OF TIMING
Congress is set to reconvene on Sept. 9. Obama said the leaders of both parties have pledged to take up and debate his request for military authorization as soon as they return.
U.N. inspectors have returned from Syria, but officials say that a report on their findings could take a week or more.
ROLE FOR CONGRESS
The Constitution gives Congress the sole power to declare and pay for war, but Congress hasn't formally declared war since World War II.
Obama as commander in chief could retaliate against Syrian targets without approval from the U.S. people or their representatives in Congress. He took a similar step two years ago in Libya. So have many other U.S. presidents.
The 1973 War Powers Act requires a president to notify Congress within 48 hours of initiating military action and bars U.S. armed forces for fighting for more than 90 days without congressional approval.