For neighbouring countries, being pulled into a war by accident after a border skirmish would be sheer folly.
Syria's fractious borders trouble its neighbours
Thursday night's shooting incident on the Syrian-Jordanian border is another ominous vindication of months of warnings: Syria's tumult threatens the very stability of its neighbours.
Armoured vehicles and infantry were reportedly involved in the clash in the Tel Shihab-Turra area, 80 kilometres north of Amman. No casualties were reported, but tensions remain high. Unconfirmed reports suggest that this was just the latest in a series of skirmishes between Jordanian soldiers and Syrian regime forces.
The struggle within Syria had already sparked bloodier incidents at and near borders with Turkey and Lebanon. Last month, Syrian rebels seized control of border crossings into Iraq, in part to facilitate the flow of arms and men.
The mesh of interconnections - geographical, cultural, tribal and political - in the region is millennia old. Now, as Syria's stability deteriorates, nearby countries cannot avoid becoming involved. The risk of regional conflict grows, with all of the attendant dangers.
There is little point in urging Syria's neighbours to show restraint; these governments have sovereign interests at stake. And as the flow of refugees from Syria increases, the pressures are growing, too.
More than 200,000 Syrians - at least 1 per cent of the population - have fled their country; 150,000 are in refugee camps in Turkey, Jordan, Lebanon and Iraq. The Jordanian border incident began with Syrian troops shooting at fleeing Syrians; the next day, a Syrian brigadier-general and two colonels reportedly defected to Jordan. There are also reports of Syrian agents prowling the refugee settlements.
Many of the refugees are Palestinians, long settled in Syria but now on the move again. In Jordan and Lebanon, this fact threatens delicate demographic and political balances.
Meanwhile, Iraqi troops sent to guard the frontier where Iraq's Kurdish region meets Syria narrowly avoided a conflict late last month with Kurdish peshmerga forces.
Turkey and Jordan, at least, are tolerating - not to say encouraging - Free Syrian Army bases and supply delivery near the border. Syria's President Bashar Al Assad will not be mourned by many neighbours. But these bases, whether or not one agrees with this limited assistance to the rebels, are a provocation to the regime; border incidents will inevitably continue.
Turkey's careful response after one of its jets was downed in June showed that the dangers of escalation are well understood. The pros and cons of deliberate intervention are debatable, but nobody can question that being pulled into a war by accident after a skirmish would be sheer folly.