So much for al Qaeda being on a path to defeat, as President Obama used to be fond of boasting. On Tuesday fighters for the Islamic State of Iraq and al-Sham, an al Qaeda affiliate known as ISIS, seized total control of the northern city of Mosul—with nearly two million people—after four days of fighting. Thousands of civilians have fled for their lives, including the governor of Nineveh province, who spoke of the "massive collapse" of the Iraqi army. This could also describe the state of U.S. policy in Iraq.

Since President...