The price for rebuilding the country, much of which has been reduced to rubble, has been reckoned at $250 billion—four times Syria’s 2010 GDP, according to the World Bank. That sum is way beyond what Russia can afford. As for future lucrative Russian arms sales to Syria, well, there’s the minor matter of how Assad will pay for them.

Russia’s gains in the rest of the Middle East have also been overblown. Moscow has, of course, been active in the conflict in Libya. But bringing order to, let alone achieving predominant influence in, a war-torn country featuring two rival governments; an ambitious military strongman, Khalifa Haftar; and a constellation of armed militias will prove a Sisyphean undertaking. Already, one of Libya’s governments has condemned Russia’s use of mercenaries there. Besides, ...