"Just when they are one year away from turning over a battered and broken enemy in both southern and eastern Afghanistan to our Afghan partners the president has now decided to deny them the forces that our commanders believe they need to accomplish their objective," McCain said.
Obama announced Wednesday night that he will pull 10,000 troops from Afghanistan by December and another 23,000 by the end of next summer.
On Thursday, the president spoke at New York's Fort Drum to troops and commanders of the Army's 10th Mountain Division. Its headquarters staff is in southern Afghanistan and its soldiers have been among the most frequently deployed in Iraq and Afghanistan over the past decade.
Obama, perhaps responding to the flank of criticism from the right, said that he is not pulling home troops "precipitously" or risking the gain they've achieved.
"We're going to do it in a steady way to make sure that the gains that all of you helped to bring about are going to be sustained," he said. "Because of you, we're now taking the fight to the Taliban, instead of the Taliban bringing the fight to us. And because of you, there are signs that the Taliban may be interested in figuring out a political settlement, which ultimately is going to be critical for consolidating that country."
Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, told the House Armed Services Committee that he supports the Obama plan, although he had recommended a less aggressive drawdown schedule.
Obama's approach adds risk to the military mission, Mullen said. But he added, "It's manageable risk."
Army Gen. David Petraeus, the top U.S. commander in Afghanistan, said later that he, too, had recommended a more gradual withdrawal as had Marine Gen. James Mattis, who as commander of U.S. Central Command is Petraeus' immediate boss and overseer of all U.S. military operations in the greater Mideast.
Petraeus, appearing before the Senate Intelligence Committee, which is considering his nomination to become CIA director, had a telling exchange with Sen. Carl Levin, D-Mich. Levin asked the general whether he would resign if he felt he could not support Obama's decision.
"I'm not a quitter," Petraeus replied. "This is something I have thought a bit about. I don't think it's the place for a commander to actually consider that kind of step unless you are in a very, very dire situation."
In the same exchange, Petraeus appeared to suggest that he had vigorously opposed the timeline that the president chose. Levin asked Petraeus whether he felt comfortable supporting the plan now.
Petraeus wouldn't sign up for that without qualification. He implied he remains uneasy about the decision but said he does not think the plan is destined to fail.
Petraeus said he was returning to Kabul on Friday to work with his staff on how to implement the Obama plan.
Obama's plan will leave 68,000 U.S. troops in Afghanistan after the drawdown. Most of those troops would gradually come home over the next two years, and the U.S. plans to close out its combat role in Afghanistan by 2015.
Secretary of State Hillary Rodham Clinton tacitly acknowledged the military had wanted more troops to remain for a longer period of time. And she said the keys to finally ending the conflict will be political negotiations with the Taliban leadership and managing a highly contentious relationship with Pakistan.
Clinton told the Senate Foreign Relations Committee that prospects for successful peace talks with the Taliban are unclear. She said the U.S. was involved in "very preliminary" contacts with the Taliban, which she said has only recently shown signs that it may be ready to talk about a political settlement.
Such contacts with enemies are distasteful but worthwhile, she said, given the historical fact that few insurgencies have been defeated without a combination of military pressure and negotiation.
"This is not a pleasant business, but a necessary one," she said.
Clinton added that she was hopeful about a political settlement. Still, she said, "We're a long way from knowing what the realistic elements of such an agreement would be."
At least as murky is the outlook for cooperation with Pakistan. Clinton said the administration is stepping up pressure on Islamabad to take more aggressive action to help eliminate extremist elements like the Haqqani terrorist network.
"When it comes to our military aid ... we are not prepared to continue providing that at the pace we were providing it unless and until we see certain steps taken," she said, noting that Pakistan and U.S. interests do not always mesh well.
Mullen, who is retiring this fall, also cited the importance of the political dimensions of the conflict. Much of the questioning from committee members, however, focused on his opening statement in which he declared his support for Obama's troop withdrawal plan while also making clear that he originally considered it a mistake.
"The president's decisions are more aggressive and incur more risk than I was originally prepared to accept," Mullen said. "More force for more time is, without doubt, the safer course. But that does not necessarily make it the best course. Only the president, in the end, can really determine the acceptable level of risk we must take. I believe he has done so."
Some in Congress have suggested that Obama was playing politics with the war plan, questioning why he would insist that the last of the 33,000 "surge" troops he ordered to Afghanistan in December 2009 leave the country by September 2012, which happens to coincide with the home stretch of his re-election campaign.
Military commanders favored a withdrawal plan that would allow them to keep as many troops in Afghanistan for as long as possible, ideally through the end of 2012
Mullen said he and the two four-star generals most directly involved in managing the war Mattis and Petraeus all support the president's plan. All three offered their views to Obama, "freely and without hesitation," Mullen said, as part of what he described as an inclusive and comprehensive White House decision-making process.
In her testimony, Clinton said it should be no surprise that U.S. commanders had pushed for a slower drawdown of troops.
"I think it would be totally understandable that a military commander would want as many troops for as long as he could get them," Clinton said. "But any military commander with the level of expertise and experience that Gen. Petraeus has also knows that what he wants is just part of the overall decision matrix and that there are other factors at work."
Petraeus said he made specific recommendations to Obama during a process that he called vigorous and inclusive.
"The ultimate decision was a more aggressive formulation, if you will, in terms of the timeline, than what we had recommended. Again, that is understandable," the general said. He did not cite specifics of his own recommendation to Obama, but he portrayed the disagreement as narrow. "We're talking about small differences."
Petraeus' designated replacement in Kabul is Marine Lt. Gen. John R. Allen, whose Senate confirmation hearing is scheduled for next week.
Afghan President Hamid Karzai on Thursday endorsed President Barack Obama's plan to withdraw 33,000 American troops from Afghanistan by the middle of next year. "The withdrawal of foreign troops from Afghanistan shows that Afghan forces have become stronger. People tell me they now have greater confidence in the security forces," Karzai said.