Republicans say their party should be credited for bringing about this milestone.
"It makes it easier to talk about fulfilling a campaign promise to wind down our operations in Iraq when the previous administration signs the security agreement with Iraq to end our overall presence there," Senate Minority Leader Mitch McConnell, R-Ky., said today. "By adopting the Bush administration's plan for winding down the war and transitioning security responsibilities to the Iraqi military over time the President has enabled us and the Iraqis to build on the gains our troops have made."
House Republican leader John Boehner, R-Ohio, gave a dueling speech this afternoon berating the president's national security policies, at the annual American Legion convention in Milwaukee.
"Some leaders who opposed, criticized, and fought tooth-and-nail to stop the surge strategy now proudly claim credit for the results," Boehner said. "Today we mark not the defeat those voices anticipated -- but progress."
Dunne says it's incorrect to label the drawdown as the ending of a combat mission. The military personnel on the ground won't engage in fighting but they are fully trained in combat missions.
"Calling it a responsible end of war or end or combat mission are both misnomers, because we still have people there putting their lives on the line and essentially doing the same thing they were doing two or three months ago," Dunne said. "I don't see a big change in the mission other than we've hit the magic number -- We've gone slightly below 50,000 troops and you can claim a political milestone and that's pretty much it."
White House officials say they are aware of the task that lies ahead, but also hailed today's announcement as a "milestone."
However, Gibbs wouldn't directly say whether Obama thought the Iraq war was worth fighting when posed the question this morning on "Good Morning America."
"I think that decision was made seven and a half years ago. Obviously putting resources into Iraq took our eye off of Afghanistan and we're now trying to make up for that even as we speak," he said. "But look, we can thank those men and women who made tremendous sacrifices. We can heal the wounds."
The White House said Obama will put the drawdown in the context of U.S. national security efforts in Afghanistan and southeast Asia. Most importantly, the president will honor those who have served and thank troops who have put their lives on the line.
"The one thing we don't argue about is the fact that we've got the finest fighting force in the history of the world," Obama today told members of the armed forces at Fort Bliss. "So the main message I have tonight and the main message I have to you is congratulations on a job well done."
Iraq war veteran Starlyn Lara, 33, said she wants the president to reassure veterans that they will not be abandoned as they struggle to deal with the trauma of war and loss of life.
"Its life changing. It definitely puts a huge strain on an individual," said Lara, whose spouse when she served in Iraq was an amputee. "It changes everyone's life."
ABC News' Luis Martinez, Kirit Radia and Sunlen Miller contributed to this report.