From Eric Schmitt and David E. Sanger, New York Times:  In the last days of November, Israel’s top military commanders called the Pentagon to discuss troubling intelligence that was showing up on satellite imagery: Syrian troops appeared to be mixing chemicals at two storage sites, probably the deadly nerve gas sarin, and filling dozens of 500-pounds bombs that could be loaded on airplanes.

Within hours President Obama was notified, and the alarm grew over the weekend, as the munitions were loaded onto vehicles near Syrian air bases. In briefings, administration officials were told that if Syria’s increasingly desperate president, Bashar al-Assad, ordered the weapons to be used, they could be airborne in less than two hours — too fast for the United States to act, in all likelihood.

What followed next, officials said, was a remarkable show of international cooperation over a civil war in which the United States, Arab states, Russia and China have almost never agreed on a common course of action.

The combination of a public warning by Mr. Obama and more sharply worded private messages sent to the Syrian leader and his military commanders through Russia and others, including Iraq, Turkey and possibly Jordan, stopped the chemical mixing and the bomb preparation. A week later Defense Secretary Leon E. Panetta said the worst fears were over — for the time being. . . .

“I think the Russians understood this is the one thing that could get us to intervene in the war,” one senior defense official said last week. “What Assad understood, and whether that understanding changes if he gets cornered in the next few months, that’s anyone’s guess. . . .”

The head of Germany’s foreign intelligence service, the BND, warned in a confidential assessment last month that the weapons could now be deployed four to six hours after orders were issued, and that Mr. Assad had a special adviser at his side who oversaw control of the weapons, the German newsmagazine Der Spiegel reported. Some American and other allied officials, however, said in interviews that the sarin-laden bombs could be loaded on planes and airborne in less than two hours. . . .

How the United States and Israel, along with Arab states, would respond remains a mystery. American and allied officials have talked vaguely of having developed “contingency plans” in case they decided to intervene in an effort to neutralize the chemical weapons, a task that the Pentagon estimates would require upward of 75,000 troops. But there have been no evident signs of preparations for any such effort.

The United States military has quietly sent a task force of more than 150 planners and other specialists to Jordan to help the armed forces there, among other things, prepare for the possibility that Syria will lose control of its chemical weapons. . . .

Syria’s chemical weapons are under the control of a secretive Syrian air force organization called Unit 450, a highly vetted outfit that is deemed one of the most loyal to the Assad government given the importance of the weapons in its custody.

American officials said that some of the back-channel messages in recent weeks were directed at the commanders of this unit, warning them — as Mr. Obama warned Mr. Assad on Dec. 3 — that they would be held personally responsible if the government used its chemical weapons.

Asked about these communications and whether they have been successful, an American intelligence official said only, “The topic is extremely sensitive, and public discussion, even on background, will be problematic.”   (graphic: Best Thinking)