Obama made very clear that this battle requires active participation by the Saudis, Turks, and Europeans. But the roles and missions haven’t yet been outlined; the commitments aren’t quite carved in concrete. The plan has a chance of succeeding in Iraq because the new government, formed by Haider al-Abadi, seems inclusive, embraced by Sunnis and Shiites, for the moment—but it could fall apart with the bombing of a single mosque or a marketplace, and then what? Will it look like the Americans are advising and bombing on behalf of a Shiite regime? Will the other Sunni nations back away, fearing the association?

As for Syria, the endgame is unclear. If the Free Syrian Army can’t get its act together, despite all efforts, will Obama step back from that terrain and focus again on Iraq—or will he be tempted to escalate and take on more of the fight alone from the air? Obama is allergic to “mission creep” (and that’s good), but he has said that this war will go on for a while; his advisers were recently quoted as saying at least three years. Where will the next president take the fight? To draw a Vietnam analogy (which, granted, should not be stretched too far), will he or she be Lyndon B. Johnson to Obama’s John F. Kennedy? (JFK sent only advisers to Vietnam, refusing to deploy combat forces.)