In public, Secretary of Defense Leon Panetta warned what was left of the regime’s leadership to protect the state’s large stockpile of chemical weapons. Privately, the U.S. intelligence community began to worry that the Syrian officials known to have the ability to authorize the use of that arsenal were now dead or gravely injured.

A scramble then ensued: who were the midlevel officers in charge of the Syrian air force and army units that controlled the stocks of sarin and mustard gas the Assad regime had been compiling for decades? And who was now running the SCUD missiles and bombers that would be deployed to use these chemical weapons? According to current and retired U.S. and Western intelligence and defense officials, U.S. analysts began to hunt for email addresses, Twitter handles, Facebook accounts, phone numbers, and Skype contacts for those midlevel Syrian officers. The information was then used to deliver a pointed message: The U.S. government knows who you are and there will be consequences if you use or transfer chemical weapons.

“The people who were killed and injured in that [July 18] suicide bombing were the people who we could try to persuade not to use this stuff,” said one congressional staffer who has been briefed extensively on the program. “When that happened, we needed to find another way to get to these guys.”