Saturday, the U.S. and Russia announced an agreement on the destruction of Syria's chemical weapons. The country has a week to detail its chemical arsenal and has until the middle of 2014 to destroy its stockpile. The State Department has published a framework for the plan.

Amy Smithson, a senior fellow at the Monterey Institute's James Martin Center for Nonproliferation Studies, gets back to the basics of chemical weapons — what they are, where they came from — with NPR's Jacki Lyden.

The Origin Of Syria's Chemical Weapons Capabilities

"Initially, the Syrian chemical weapons program was very dependent on outside expertise and materials coming in from the outside," Smithson says.

In the 1990s Syria appears to have received assistance from Iran and Russia in the form of the "precursor chemicals" (ingredients for the weapons) as well as technical support, she says, "and North Korea also came into the equation then with assistance on delivery systems."

"But quite some time ago, the program appears to have transitioned to one where Syria has the domestic capacity to do all this," Smithson says. "In other words, they have production facilities, apparently, for them that are capable of making chemical warfare agents."

What Counts As A Chemical Weapon?

The Organisation for the Prohibition of Chemical Weapons, or OPCW, defines chemical weapons as "any toxic chemical or its precursor that can cause death, injury, temporary incapacitation or sensory irritation through its chemical action."

The delivery devices for the chemicals, filled or unfilled, "are also considered chemical weapons themselves."

Smithson says there are two basic forms of chemical weapons: unitary and binary. Those classified as unitary are already mixed before being loaded into munitions.

With binary weapons, the last two precursor chemicals can be mixed at the last minute and then loaded into the munition. Or those chemicals can be stored separately inside of the munition, and on the way to the target, the membrane between the chemicals bursts, creating a deadly mixture.

In terms of making the weapons, Smithson refers to the saying, "A bozo can make it in a beaker."

"To make the chemical warfare agents, a chemist with fairly rudimentary experience is probably going to be able to synthesize a small quantity of these agents," she says. "But to scale up to large quantities, the types of things that militaries often have to have in order to use them on the battlefield, that's a whole other ballgame."

The Daily Beast published an article in August, a few days after the chemical attack in Syria, breaking down the types of chemical weapons that have been used historically.

How To Inspect, Destroy Chemical Weapons

When inspectors are sent into a country, they inspect production facilities and storage sites to first take inventory, Smithson says.

"So they're literally going to be in the field counting munitions and closing down production facilities. Out of that, there will be a determination made about what destruction processes would be best for this particular arsenal," she says.

One of their most important jobs, Smithson says, is watching the weapons being destroyed.

"They also go to commercial facilities that produce significant quantities of the chemicals that can feed into a chemical weapons program, but under legitimate circumstances are in the products that we make use of in our homes and lives every day," she says. (The OPCW goes into more detail about the issue of balancing these possible uses with their potential to harm.)

Libya's Moammar Gadhafi agreed to give up the country's chemical weapons in 2003, a process with lessons for future weapons dismantling.

Former U.N. weapons inspector Charles Duelfer discusses the challenges specific to Syria with Scott Simon, host of Weekend Edition Saturday.

How U.S. Position Has Evolved On Chemical Weapons

Modern chemical warfare is traced back to World War I. The Geneva Protocol, prohibiting the use of chemical and biological weapons in war, was signed in 1925. But the U.S. didn't ratify it until 1975.

"And when it did, it reserved the right to retaliate in kind if chemical weapons were used against U.S. forces. That's largely because this was Cold War-era, and the Soviet Union had a large chemical weapons program," Smithson says.

The U.S. position changed again in 1991, when President George H.W. Bush publicly renounced the right to retaliate in kind.

The international Chemical Weapons Convention was adopted in 1992.

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