“At the end of the day,” an exhausted senior State Department official said, wrapping up three days of round-the-clock negotiations with Russia over the disposal of Syria’s chemical weapons arsenal, “the things that most mattered, I believe we got.”

Aides to Secretary of State John Kerry said he and his Russian counterpart, Foreign Minister Sergey Lavrov, joined by teams of technical advisers, intelligence and military officers, lawyers and policy experts, slogged through “hard-fought” talks that did not, in the end, result in complete agreement.

For example, the two delegations never came to terms on exactly how many sites the regime of Syrian President Bashar al-Assad uses to produce, mix, and store chemical weapons, nor on whether all of those sites are in areas that remain under regime control, as the U.S. maintains, and Russia denies.