The use of chemical weapons in Syria has increased pressure on U.S. President Barack Obama to arm the opposition. Instead, the United States should focus on working with Russia to disarm Syria. A U.N. Security Council resolution mandating an inspection and disarmament process for Syria could open the door to wider negotiations on a political resolution.

I have long advocated arming opposition movements that resist dictatorships and aggression. The strategy yielded major gains during the Soviet-Afghan war, in Bosnia, in Afghanistan in 2001 and during the Libyan revolution, all without unduly exposing the United States. There is good reason to believe that Washington erred in withholding more lethal assistance from the Iraqi opposition to Saddam Hussein. And arming friendly non-state actors may prove prudent in dealing with the fallout of the Arab Spring in some contexts.

In Syria, however, failure to arm the opposition when the uprisings began two years ago has allowed extremist forces to gain the upper hand. Liberal and secular movements have largely gone into exile, leaving a vacuum that extremists are exploiting. Obama, so keen to internalize the lessons of the Iraq war, should have understood that protracted conflict was unlikely to favor moderates. Bashar Assad's brutality has radicalized the Syrian people, who only recently were committed to nonviolent resistance to his dictatorship. Islamist forces — some with ties to al-Qaida — have become the key element of the opposition, if not its backbone.