John F. Kerry was late to his own party. Staffers, journalists and other officials were gathered in the ornate Benjamin Franklin salon at the State Department on Dec. 14 for early Christmas festivities. But the secretary of State was nowhere to be seen. Kerry was on the telephone to various world leaders, trying to find out about a major diplomatic meeting — from which the United States had been excluded. The gathering, which sought to broker a resolution to the devastating Syrian conflict, took place six days later in Moscow and involved the foreign ministers of Russia, Iran and Turkey.