RIGHT SPEAK: Charles Krauthammer op-ed: A Battle against Barbarism

Baghdad called President Obama’s bluff and he came through. He had refused to provide air support to Iraqi government forces until the Iraqis got rid of their divisive sectarian prime minister.

They did. He responded.

With the support of U.S. airstrikes, Iraqi and Kurdish forces have retaken the Mosul dam. Previous strikes had relieved the siege of Mount Sinjar and helped the Kurds retake two strategic towns that had opened the road to a possible Islamic State assault on Irbil, the capital of Kurdistan.

In following through, Obama demonstrated three things: the effectiveness of even limited U.S. power, the vulnerability of the Islamic State and, crucially, his own seriousness, however tentative.

The last of these is the most important. Obama had said there is no American military solution to the conflict. This may be true, but there is a local military solution. And that solution requires U.S. air support.

It can work. The Islamic State is overstretched. It’s a thin force of perhaps 15,000 trying to control a territory four times the size of Israel. Its supply lines are exposed and highly vulnerable to air power.

Stopping the Islamic State’s momentum creates a major shift in psychology. Guerrilla armies thrive on a sense of inevitability. The Islamic State has grown in size and attracted recruits from all over the world because it seemed unstoppable, a real caliphate in the making.

People follow the strong horse over the weak horse, taught Osama bin Laden. These jihadis came out of nowhere and shocked the world by capturing Mosul, Tikrit and the approaches to Kurdistan, heretofore assumed to be impregnable.