The only means available to the US to assume a responsibility to protect the Syrian people from slaughter was by credibly threatening Bashar al-Assad and the security and military elite surrounding him with a decapitating air strike if they did not immediately cease murdering protestors and begin negotiations with opposition figures to the end of making the regime broadly representative of the Syrian population. Credibility probably demanded an initial decimation, a technically possible move. In part because the US lacks the ideology and institutional structure of a real imperial power, in part because it is post-Bush a careful calculator of national interests, Syria, unlike Libya but much like Sudan and the DRC, was a bridge too far.