CNN News:追踪叙利亚内战 化学武器成焦点

We're starting with an update on the civil war in Syria. We've been covering this since 2011 when that war begun. It involves the Syrian government that's fighting to hold to power, rebel groups that are trying to overthrow the government, terrorist groups who are trying to expand their power in Syria. It also involves the United States, which is using Special Forces and airstrikes against terrorists, as well as Russia, which is launching airstrikes in supporting Syria's current government.
Since 2011, more than 250,000 Syrians have died in their nation's civil war and one site of some of the worst fighting and destruction is the Syrian city of Aleppo. It used to be the country's most populated city.
To date, part of it is controlled by government troops, part controlled by rebels, and United Nations officials are trying to figure out if an attack on the rebel-controlled part of Aleppo involved chlorine gas. That's a chemical weapon. Rebels and doctors in the area say at least three people died in an apparent chemical attack.
The Syrian government has been accused of using chemical weapons before in this civil war. The government denies it. But this is significant because chemical weapons are illegal, even in war.

JIM SCIUTTO, cnn CHIEF NATIONAL SECURITY CORRESPONDENT: Chemical weapons are known as the "poor man's atom bomb", because at relatively cost, they could have devastating effect, both in terms of casualties, but also in the sheer horror of the injuries and the sheer fear of contamination.
In the history of warfare, they've been used very seldom. You have to go back to World War II for widespread use, although Saddam Hussein used in the late 1980s, killed some 5,000 people in northern Iraq, in Kurdistan. More recently, the Assad regime has used them repeatedly in the war in Syria. It's estimated, some 1,500 people have been killed, 15,000 injured in chemical weapons attacks in Syria.
The Geneva protocol of 1925 banned the use of chemical weapons in warfare, but not the production. It was until the early 1990s that the Chemical Weapons Convention banned the production and stockpiling as well, and since then, some 90 percent of the world's chemical weapons have been destroyed.
But still, to this day, there's a lot out there in 17 countries still have them from the ones you'd expect, North Korea for instance, which did not sign on to any of those treaties, but also the U.S., although the U.S. has committed never to use them in warfare and is committed to destroy all of them by the 2020s.