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On Feb. 10, U.S. Vice President Joseph Biden gave an interview to CNN. Most of the next day's headlines predictably focused on his assessment that al Qaeda probably isn't capable of mounting another 9/11-style attack. What garnered far less attention was his take on Iraq. "You're going to see 90,000 American troops come marching home by the end of the summer," he declared. "You're going to see a stable government in Iraq that is actually moving toward a representative government." He predicted that the withdrawal would count among the "great achievements of this administration."

Perhaps these claims are not surprising. President Barack Obama himself declared the war as good as over in his January State of the Union address. U.S. casualties have dropped sharply over the past two...