The killing of 200 people in the village of Tremseh has confirmed the depth of the Syrian crisis and the dangers it poses for the region; it has also exposed major problems for international institutions. In Tremseh, one of the bloodiest episodes since the uprising started in 2011 occurred on July 12 when, according to United Nations observers, heavily armed government forces targeted rebels and defectors. A week later, a suicide bomber killed defence minister Daoud Rajha, his deputy Assef Shawkat, who was also President Bashar al-Assad’s brother-in-law, and former defence minister Hassan Turkomani; a fourth victim, national security chief Hisham Ikhtiar, died later from his injuries. That the attack took place at the National Security Bureau in Damascus is a huge blow to the Ba’ath regime. Fighting continues in Damascus, and thousands of civilians have already tried to take shelter in a Palestinian refugee camp at Yarmouk, a southern district of the city. In a further key development, Russia and China have for the third time vetoed a Syria-related U.N. Security Council resolution, with Russia rejecting sanctions and military intervention; Moscow also accuses the western powers of blackmailing it with threats to block the renewal of the U.N. Supervision Mission unless it collaborates over Syria.

The violence there, which has claimed 17,000 lives so far, is itself terrible, but the inability of the international community to reach any kind of agreement means the crisis will almost certainly escalate even further. That Mr. Assad is in deepening trouble is not in doubt. Senior-level defections from his regime are becoming more frequent, and the rebels now hold five border crossings, four to Iraq and one to Turkey. Nevertheless the prospects for post-Assad stability do not look bright. The United States, in the person of its U.N. Ambassador Susan Rice, says it will work outside the Security Council to put pressure on the regime; this is ominously reminiscent of the prelude to the illegal Iraq invasion in 2003. Second, there is increasing evidence of tension among the rebels resulting from the increasing involvement of extreme Islamists sponsored by West Asian Sunni-majority states, which have also provided sophisticated weapons of western manufacture. None of the external players is showing any motivation beyond self-interest. If Russia and China are concerned about the fate of the Assad regime, the U.S. and its allies are not willing to draft a balanced resolution that pushes regime opponents towards talks. Unless the big powers give up their games, Syrian civilians will continue dying by the thousand.

More In: Editorial | Opinion