By naming Petraeus, President Barack Obama managed to replace Gen. Stanley McChrystal without derailing the mission at a critical juncture in the war, when casualties are rising and public support in the West is waning.
Still, the jury is out on whether the counterinsurgency strategy that Petraeus used to turn around the Iraq war will show results in Afghanistan by July 2011, when Mr. Obama wants to begin withdrawing U.S. troops.
The split between the U.S. civilian and military team in Afghanistan has not disappeared with McChrystal's departure. Those fissures, laid bare in disparaging remarks to Rolling Stone magazine, led to McChrystal's dismissal Wednesday.
Petraeus inherits myriad challenges. Among them:
• Eighty international troops have died so far this month, making June the deadliest month of the nearly 9-year-old war.
• A major offensive in Helmand province earlier this year has yielded mixed results. McChrystal himself acknowledged that the security campaign already under way in neighboring Kandahar province is going more slowly than expected.
• While NATO has worked hard to train a growing number of Afghan soldiers and police, their ability to go it alone without their more skilled NATO partners at their side has yet to be tested.
The politically savvy Petraeus probably would have a better shot at convincing Mr. Obama that the strategy needs more time and slow the withdrawal of U.S. troops. Petraeus helped train the Iraqi army and is on a first-name basis with defense officials in capitals that provide troops to the NATO-led force in Afghanistan.
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Initially, NATO leaders in Brussels played down the Rolling Stone article, which suggested that powerful players in the Obama administration still disagree on the unproven U.S. counterinsurgency strategy of routing the Taliban, securing major population centers, bolstering the Afghan government's effectiveness and rushing in aid and development.
They were relieved when Mr. Obama selected Petraeus, who pioneered the same basic counterinsurgency strategy when he commanded U.S. forces in Iraq.
"The strategy continues to have NATO's support and our forces will continue to carry it out," NATO Secretary-General Anders Fogh Rasmussen said in a statement. "We will stay for as long as it takes to do our job."
Retired Brigadier Gen. Anthony Tata, who served under both McChrystal and Petraeus said Petraeus' transition to Afghanistan command would be "seamless."
"Relationships are everything in this part of the world. … Petraeus has good relationships with Karzai, the Pakistani leaders … that's key," Tata said on CBS' "The Early Show", adding that Petraeus also had strong relationships with the Obama administration's civilian leaders in the country.
Tata also note the importance of training the Afghan police and armed forces - an "Achilles heel" for the country's security, he said.
"That's the key with petraeus here," he said.
Some critics have questioned whether a strategy aimed at bolstering the Afghan government can ever succeed in a country with ethnic divisions and a history of tribal rule.
"The situation in Afghanistan is in obvious disarray and it's not because of personnel. It's because of policy," said U.S. Rep. Dana Rohrabacher, R-Calif. "The frustration expressed by McChrystal and his aides highlights the failure of our current policy in Afghanistan."
Despite those doubts, there is simply not enough time to recraft the strategy before Mr. Obama's July 2011 withdrawal date.
"This is not the time for a new commander to come in to rethink strategy," said Malcolm Chalmers of Britain's Royal United Services Institute, a British think tank.
The prospect of having to deal with a third NATO commander in little over a year was an unwelcome prospect for Afghan leaders, who had spent months building rapport with McChrystal, the lanky commander who had become President Hamid Karzai's most trusted U.S. partner.
They had expressed hope that Mr. Obama wouldn't fire McChrystal, but in the end, internal U.S. politics trumped their desires.
"Gen. McChrystal was a fine soldier and a partner for the Afghan people," Karzai spokesman Waheed Omar said. "But we believe Gen. Petraeus will also be a trusted partner."
Omar said the Afghan leadership hoped replacing McChrystal would not impede progress in the war.
"We know Gen. Petraeus. He knows the country. He knows the strategy," Omar said. "He is the most informed person and the most obvious choice for this job."
The sentiment was echoed in Western diplomatic circles in Kabul, where foreign officials were skittish about prospects of a McChrystal departure - 13 months after Defense Secretary Robert Gates sacked Gen. David McKiernan, saying the mission needed a fresh approach.
Vygaudas Usackas, head of the European Union delegation in Afghanistan, said McChrystal was the right man at the right time for the job.
"I think he really was a pioneering commander for changing the paradigm of the military engagement in Afghanistan to being about protecting the people and talking to communities," Usackas said, adding that he didn't think the switch would disrupt the mission. "Stan has done a tremendous job. He was a great leader. He made a mistake - a big mistake."
The NATO headquarters in Kabul was quiet throughout the day, waiting for Mr. Obama's decision. The staff knew McChrystal could lose his job but were stunned when it actually happened. Troops and civilians working there said an unsettled mood during the day turned somber when they learned they'd lost their leader.
Senior officials quickly preached the need for a smooth changeover in command.
"The campaign remains on course," said Mark Sedwill, NATO's senior civilian representative to Afghanistan.
A top official told his staff that while they'd lost a good commander, they should focus on the troops risking their lives to bring stability to the nation. One of those at the meeting, speaking on condition of anonymity because the discussion was private, said the message was "We can't let this campaign skip a beat."
In Baghdad, an Iraqi government spokesman said he didn't expect the change to affect the withdrawal of U.S. troops from that country.
"The American administration is concentrating on Afghanistan because the security situation there is more critical than Iraq," Ali al-Dabbagh said. "Iraq has overcome the critical stage and our troops now are more qualified" to take charge.
The greatest fallout from the McChrystal controversy is the perception it creates in the minds of Afghan citizens, said Nader Nadery, deputy director of the Human Rights Commission in Kabul. He fears it will convince Afghans that the NATO mission is not led by a united team of professionals but by a U.S. team seemingly at war with itself.
"It is certainly not helpful," he said. "The Taliban will create the perception among people, saying: 'Look, they are not going to win. They are all in disagreement.'"