There have also been about a half-dozen U.S. generals who only commanded American combat troops in the first years of the conflict.
By comparison, the command tours of generals in Iraq ‘‘averaged almost twice as long as ISAF's,’’ said Stephen Biddle, a professor of political science and international affairs at George Washington University.
Given the huge funds involved in the war effort, running the Afghan campaign has been as complicated as managing a multibillion dollar corporation.
Anthony Cordesman, a national security expert at the Center for Strategic and International Studies, said the lack of continuity includes both the military and civilian presence in Afghanistan, including the State Department and other agencies.
‘‘What the Afghans see is constant change at every level,’’ he said. ‘‘They constantly see people come and go. They have no reason to establish lasting relationships. People leave at the point where they’re becoming most effective.’’
He added that ‘‘this constant rotation is a problem everybody recognizes, but no one has really been willing to address.’’
The Pentagon also has a number of senior leaders — ranging from the chairman of the joint chiefs of staff and defense secretary to the commander of U.S. Central Command — who also play key roles in the war strategy and provide some continuity.
‘‘There is no doubt that the frequent changeover is tough. There is a learning curve each time a new man takes the helm,’’
‘‘The good aspect to this is that it brings a fresh set of eyes,’’ said Michael O'Hanlon, a fellow at the Brookings Institution in Washington. ‘‘It’s not realistic to have commanders serve a whole lot longer than, say, Gen. Allen ... as these folks get tired.’’
Baldor reported from Washington. Associated Press writers Rahim Faiez and Deb Riechmann in Kabul contributed to this report.