Somalia is a cautionary example for those who, like Barack Obama, favor rapidly withdrawing U.S. forces from Iraq and managing any threat from al-Qaeda with an “over the horizon” strike force. Such forces indeed have the ability to target and kill leaders. They do nothing, however, to change the conditions under which al-Qaeda finds refuge and recruits. As Gen. David H. Petraeus is demonstrating in Iraq, successful counterterrorism requires providing security for the civilian population, economic reconstruction and the brokering of political accords — in other words, nation-building. That’s as true in Somalia as it is in Iraq.