Another irony is that the most successful reversal of Bush’s counterterrorism agenda that Obama managed to achieve is arguably the one that has brought him the most grief: the end of the U.S. war in Iraq. The Bush administration made many different arguments—often based on flawed or misleading intelligence—for why the United States had to invade Iraq. But all of them were rooted in an increased feeling of vulnerability produced by the 9/11 attacks; in that sense, although many factors contributed to the invasion, it must be considered a centerpiece of Bush’s “war on terror”—and it was the element of Bush’s counterterrorism policy to which Obama most strongly objected.