Syrian scientists showed them rooms with test tubes, Bunsen burners and desktop computers, according to inspectors. The Syrians gave a PowerPoint presentation detailing the medical and agricultural research they said went on there. A Syrian general insisted that the Assad regime had nothing to hide.

As the international inspectors suspected back then, it was a ruse, part of a chain of misrepresentations by President Bashar al-Assad’s regime to hide the extent of its chemical-weapons work. One year after the West celebrated the removal of Syria’s arsenal as a foreign-policy success, U.S. intelligence agencies have concluded that the regime didn’t give up all of the chemical weapons it was supposed to.

An examination of last year’s international effort to rid Syria of chemical weapons, based on interviews with many of the inspectors and U.S. and European officials who were involved, shows the extent to which the Syrian regime controlled where inspectors went, what they saw and, in turn, what they accomplished. That happened in large part because of the ground rules under which the inspectors were allowed into the country, according to the inspectors and officials.