WAR WITHOUT WAR: Sanctions have grown in popularity since the end of the Cold War as an alternative to armed conflict. They enable governments to take a stand without placing their soldiers in harm's way. In Syria, Libya-style military intervention is not in the cards. So the United States and its Western allies have turned to economic sanctions as a way to promote political change.

WINS AND NOT-WINS: Sanctions sometimes backfire, deepening the suffering of ordinary people, prolonging a conflict by stiffening the resolve of autocratic governments or even triggering war, as when the U.S., Britain and the Netherlands imposed an oil and steel embargo against Japan in 1941. In the most successful cases — such as sanctions in support of black majority rule in Africa or promoting democracy in communist Poland — it took years to achieve the goal.

THE MATH: a 2007 study by three scholars at the Peter G. Peterson Institute for International Economics found that sanctions were successful in undermining or changing a regime in only about 34 percent of the cases. Some argue even that figure is too high because the study included successful cases where military force was also used. Still, economic sanctions remain popular because they are the "only coercive measures available to the international community" short of the use of force, as Jeremy Greenstock, a former British ambassador to the United Nations, wrote before the Iraq war.