In Northern Ireland it used to be called "the politics of the last atrocity", when the latest act of violence and the retaliation it provoked dictated the direction of day-to-day politics. Syria has travelled far in this direction, its towns convulsed by mini-civil wars too bitter and bloodstained to end by mediation.

It is this which is making it so difficult for Kofi Annan, joint envoy for the UN and Arab League, to succeed in his mission. The Syrian government has demanded guarantees from the militiamen it is fighting that they will abide by a ceasefire. This is unlikely to happen given the total distrust between the two sides and with the insurgents fearful of risking torture and execution.

The skirmish on the Syrian-Turkish border is an example of the problems facing any attempt to end the fighting. Anti-government forces attacked a Syrian government checkpoint near the frontier, killed six soldiers and were then shot at as they retreated across the frontier, with bullets hitting dwellings in a nearby refugee camp.

Could this provoke Turkish intervention in the shape of a safe haven for refugees? Ankara has so far been unwilling to risk an all-out conflict. Both sides are playing to the gallery, the insurgents trying to publicise any action by the Syrian army that might goad foreign powers into action. Mr Assad needs to make a show of moderation to keep Russia and China on side.

So far it is the differences between Libya and Syria which are most striking. In Syria, Nato countries want an excuse not to do anything radical, while in Libya they were looking for a justification to intervene. And without direct action by foreign powers, the only alternative for the Free Syrian Army is to wage an escalating guerrilla war against Bashar al-Assad's government which is unlikely to bring about a collapse of the regime.

Mr Assad's options are also limited. He and his government have survived a year of pressure. During fighting in and around Homs, the Syrian army showed that it could crush any insurgent band.

But the government's brutality, including torture, summary executions and artillery bombardments of civilian areas, means it is always creating fresh enemies.

Diplomats say Mr Assad's senior officials are in a confident, and possibly an over-confident, mood. They may have stopped the tide of insurgency, but they will be unable to reverse it. Concessions made last spring might have had an impact, but since then too much blood has been spilled.