One of the defining features of Gen. David Petraeus' tenure as leader of U.S. forces in Iraq is an unusually close partnership with his political counterpart here, Ambassador Ryan Crocker.
With that connection about to be broken, the question arises: Will it matter at this calmer but still fragile stage of the war?
Petraeus, widely credited as chief orchestrator of a generally successful counterinsurgency strategy, is due to depart in September. Crocker, among the State Department's most experienced Middle East hands, says he will stay until President Bush leaves the White House in January, then retire.
In an Associated Press interview, Petraeus said he and Crocker saw "inescapable merit" in a political-military synergy. So when they arrived in Baghdad in early 2007, with sectarian violence still raging, they wrote and then executed a classified "joint campaign plan" for countering the insurgency.
Petraeus, Crocker and others insist that the changeover in September need not disrupt the momentum that has been generated over the past year toward stifling the insurgency and getting Iraq on a path toward stability.
Asked in an AP interview last week whether he was worried about the loss of Petraeus, Crocker said, "Not at this stage." He noted that in Petraeus' new job as commander of U.S. Central Command he will remain connected to Iraq policy as overseer of all U.S. military operations in the Middle East.
But personalities - not just skill and experience - count in a conflict like Iraq's, with its complex web of political, military, economic and social pitfalls. Close observers of the war see Petraeus and Crocker as exceptional, possibly even pivotal figures. But doubts about the effect of their departure are muted.
Barry McCaffrey, a retired four-star Army general who visits Iraq periodically to assess war progress, said in an interview in early July that finding the right person to succeed Crocker may be the key.
"It's hard to imagine how you replace Crocker," McCaffrey said. "This guy is really unusual. I've watched ambassadors for 15 years now in a global context. He's the best I ever saw," not only because he dealt effectively with Iraqi political figures and formed an exceptionally close partnership with Petraeus, but also because he managed to generate an unusual level of loyalty inside the U.S. Embassy.
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One legacy of the Petraeus-Crocker partnership is that the new U.S. Embassy in Baghdad, to be fully occupied later this year, has been configured to replicate the arrangement in the existing embassy with the ambassador's office next to the U.S. commander's. They share a visitors waiting room.
In the final months before the White House changes hands - the first wartime transition in 40 years - Crocker will be working with Gen. Ray Odierno, who is preparing to succeed Petraeus in Baghdad. Odierno served in command twice before in Iraq - first in 2003-04 as commander of the 4th Infantry Division and again in 2006-08 as the No. 2 overall commander. Since February he has been at Fort Hood, Texas, and this summer is closely monitoring the full range of developments in Baghdad.
Stephen Biddle, a military analyst at the Council on Foreign Relations and an occasional adviser to Petraeus, said in an interview that he, too, thinks a key will be a Crocker successor whose personality gels with Odierno's.
"It's kind of a shame" that these changes come now, Biddle said. "The chemistry was remarkably good and extremely helpful. If I were the president I would be thinking about not just getting a very able diplomat to do that job but getting someone who gets along with Ray Odierno and is willing to spend as much time with him as Petraeus spent with Crocker."
Asked in the AP interview about his successor, Petraeus said, "He knows the ambassador very well and I'm sure they will be very comfortable."
A representative of Odierno's commander's initiative group - a kind of internal think tank - is present in Baghdad, participating in all of Petraeus' sensitive meetings, Petraeus says, and relaying information to Odierno.
Odierno has been criticized for what some saw as overly aggressive tactics during the earliest stages of the insurgency, but his performance in 2006-08 has generally been praised as a nuanced application of counterinsurgency doctrine. He also has had a recent hand in the diplomatic world, having acted as the chairman of the Joint Chiefs of Staff's main link to the State Department in 2004-06.
Amid these top-level changes, a figure of stability in Baghdad will be Lt. Gen. Lloyd Austin, the No. 2 overall commander, who succeeded Odierno in that post in February. And while Defense Secretary Robert Gates - also seen as a key figure in the military's more successful approach in Iraq since early 2007 - is due to leave in January, the chairman of the Joint Chiefs of Staff, Navy Adm. Mike Mullen will remain.