When military officers and diplomats gathered in a secure room in the Pentagon on a recent Friday to get a video briefing from the Afghan battlefield, they were startled to see a youthful British diplomat in an open-neck shirt, rather than the familiar face and camouflage fatigues of Gen. Stanley McChrystal, the American commander. The diplomat's name is Mark Sedwill, the new senior civilian representative of NATO in Afghanistan, and on that day, he was acting as McChrystal's proxy. It is a role Sedwill, 45, has taken on with increasing regularity in recent weeks, forging a tight relationship with the general that associates say carries echoes of the one in Iraq between Gen. David Petraeus and the American ambassador in Baghdad, Ryan Crocker. Their mission also bears striking similarities to the 'surge' those men carried out in Iraq: forging a combined military-civilian offensive to drive out a stubborn insurgency and allow a competent local government to take root. As the protracted struggle to bring order to the southern Afghan town of Marjah demonstrates, it has been an uphill battle so far. The two men travel together every other week to hot spots around Afghanistan. They often team up to visit President Hamid Karzai. And with McChrystal's support, Sedwill has turned what had been a low-profile adviser's role into a key civilian leadership post -- one in which he vies for visibility with the American ambassador in Kabul, Karl Eikenberry. 'Partly because of his interpersonal skills and partly because of his backing by McChrystal, he has emerged very fast,' said Richard Holbrooke, the Obama administration's special representative to Afghanistan and Pakistan. 'McChrystal immediately and with great skill began using Sedwill as his political arm, thus improving his effectiveness.' Inevitably, Sedwill's rise raises questions about the relationship between McChrystal and Eikenberry, a retired general who was once himself the commander in Afghanistan. Both men insist that they work closely together, too, and that reports of tension between them are inaccurate. With a multinational coalition like that in Afghanistan, Eikenberry said, it is essential to have non-Americans in leadership posts. 'That's a very powerful signal that this is a true alliance,' he said, adding that Sedwill was an 'absolutely superb diplomat.' A career member of the British Foreign Office who once worked as a U.N. weapons inspector in Iraq, Sedwill first crossed paths with McChrystal in 2009 when he was the British ambassador in Kabul. McChrystal had just assumed command of the International Security Assistance Force, the combined NATO and American presence in Afghanistan. 'We kind of hit it off personally, straightaway,' Sedwill said in a telephone interview from Kabul. McChrystal was traveling this week, his aides said, and unavailable for an interview. Referring to the general's ascetic lifestyle, Sedwill said, 'We've obviously got very different backgrounds. I certainly eat more than him; I sleep less than him. I hit the gym, but not as much as he does. As far as an undisciplined diplomat,' he joked, 'I'm about as close to Stan as I could be.' Sedwill expanded what had been a sleepy NATO civilian operation under his predecessor, Fernando Gentilini, an Italian diplomat. Gentilini had a staff of just six people; under Sedwill, the staff is expanding to 24, drawn from the United States, Britain, Denmark, Canada and Australia. His goal, he said, is to better coordinate NATOs far-flung civilian operations so that the so-called provincial-reconstruction teams sponsored by European countries in Afghan districts work more closely with one another and with the local Afghan authorities. As a British diplomat, it is easier for Sedwill to press fellow Europeans than it would be for an American. NATO officials said he had ruffled feathers among some European countries for criticizing the way they ran their civilian operations. Sedwill 'is not shy about poking some of NATO's sacred cows,' a senior alliance official said, speaking on condition of anonymity because of diplomatic protocol. Sedwill said he was trying to get the civilian teams to help the local Afghan authorities deliver services rather than doing it themselves. That would address what he conceded was a hurdle in the campaign so far: the lack of trust Afghans have in their government. In Marjah, for instance, the troops drove out the Taliban with little trouble, but the Afghans and Americans have struggled to put a credible local government in place. 'If I can claim credit for anything, it is for really getting people involved in the political issues that fuel the process,' he said. 'The language we now use is that we talk about a political campaign with a military phase.' Sedwill is trying to apply the lessons from Marjah to Kandahar, a much larger city with a more complex political landscape. There, a big question is how to deal with Karzai's brother, Ahmed Wali Karzai, the head of the Kandahar provincial council and a divisive figure whom many American and Afghan officials accuse of having ties to drug traffickers and Taliban insurgents. 'Ahmed Wali plays a very powerful role,' Sedwill said. 'We're in a close dialogue, and are encouraging him to use his influence, his power, to build a genuine political deal.' While it may be too much to suggest that McChrystal engineered Sedwill's appointment, NATO officials said he clearly made his preference known when other candidates' names surfaced first. Sedwill's emergence also laid to rest a long-simmering debate over how to structure the civilian leadership of the Afghan campaign. The United States had initially wanted to install a powerful viceroy who would have functioned as a counterpart to the military commander. Previous efforts to install a powerful civilian chief had foundered because of Hamid Karzai's objections and European fears that a viceroy would dilute the authority of the United Nations' special representative. Now, Sedwill fills out what Holbrooke described as a quartet of civilian leaders: Eikenberry; Staffan de Mistura, an Italian-Swedish diplomat who represents the United Nations; and Vygaudas Usackas, a Lithuanian who is the European Union's special representative. Of these four, though, only Sedwill can call himself McChrystal's wingman. 'I wouldn't have taken the job if I hadn't been confident in my relationship with McChrystal,' he said. 'He probably would have sought to block anyone he didn't have confidence in.' 