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Fouad Siniora, Lebanon’s former prime minister, is a thoughtful man with deep experience in Middle Eastern politics. So when he speaks of “trains with no drivers that seem to be on a collision course,” as he recently did at a private meeting in Berlin, interested parties should probably prepare for unwanted developments. Of course, no one in the region is calling for war. But a pre-war mood is growing.

Four factors, none of them new but each destabilizing on its own, are compounding one another: lack of hope, dangerous governmental policies, a regional power vacuum, and the absence of active external mediation.