The quest for a constructive step by concerned nations on the increasingly lethal, seemingly inconclusive Syrian civil war has come down to a conference, brokered by Russia and the United States, that would put the Syrian adversaries face to face at a table to discuss their differences.
That was the outcome of a visit that Secretary of State John F. Kerry just completed to Moscow, where he met with President Vladimir V. Putin and Foreign Minister Sergey V. Lavrov.
The barriers to such a conference, however, are formidable. They include Russian reluctance to jeopardize the future of their ally, Syrian President Bashar Assad. Part of Russia's reasoning in protecting it has been its sense that the United States and the West want to get rid of the Damascus regime. It would nonetheless be up to the Russians to get Mr. Assad to a table, one where his own future would be a principal subject of discussion.
On the rebel side, the barrier to a conference would be the diversity and intractability of their own opposition elements. Who would speak for them? Can anyone speak for them? The "Syrian opposition" consists of everything from groups favorable to the United States and the West, to Iranian-controlled groups, to al-Qaida-oriented Sunni Islamists who would like to see the U.S. government fall almost as much as they would like to demolish the Assad regime.
Mr. Kerry's efforts to improve U.S. relations with Russia, including during this trip, have no doubt played a role in the more constructive approach to Syria that Mr. Putin's government may be ready to take. It is quite likely that America's tragic experience in Boston with bombers of Chechen ancestry, reinforcing Russia's longtime position that Caucasus Islamists include some vicious terrorists, may have helped improve U.S.-Russian dealings.
If an outcome of Boston were to be a constructive conference on Syria, that would be a silver lining to a very dark cloud.