THE partial cease-fire in Syria’s civil war is welcome news. But it must not be allowed to obscure a dangerous new development — the emergence from the war of a Russian-Iranian military axis that could upset hopes for stability in the Middle East, and for containing Russia’s global ambitions.The US and Russia are nowhere near a new Cold War but the US has every interest in discouraging Russia’s and Iran’s impulses to ally themselves in rivalry with the West.Such an alliance would guarantee a more intractable Iran, projecting power in the Middle East as an assertive Russia tried to restore its sway along its own rim. Fortunately, it is still early in the game. First, the United States must move more effectively to end Syria’s war. The cease-fire could be useful for this, but only if American diplomats insist on using the pause to open serious discussions toward a political settlement.