The comments were made to a House panel by Army Gen. Martin Dempsey. Earlier, Defense Secretary Chuck Hagel said the battle against Islamic State militants would be "long and difficult."
The six-week battle to retake the city from insurgents was the fiercest during the Iraq War. Almost 100 Americans died; 600 others were injured. Veterans commemorated the anniversary on Friday.
George W. Bush also uses the new book to reflect on his own legacy. On Wednesday's Morning Edition you can hear his thoughts about his decisions on Iraq and the current situation there.
Former President George W. Bush discusses with NPR's David Greene how both he and his father, former President George H.W. Bush, waged war against Saddam Hussein, and the state of Iraq today.
A vocal critic of the Iraq war and the Bush administration has died. In 2004, Army veteran Tomas Young deployed to Baghdad, where a bullet left him paralyzed. Young passed away at his home in Seattle.
In an update to a 2011 StoryCorps interview, retired Army Sgt. 1st Class Max Voelz, whose wife died disarming an IED, and Sgt. Mary Dague, who lost both arms in Iraq, both say they are happy now.
With Iraq's military in tatters and U.S. forces gone, the Kurdish peshmerga is the only viable force to stave off ISIS in Iraq. With little support from Baghdad, discontent grows among the fighters.
Airstrikes against ISIS have had some success. But James Jeffrey, Obama's former ambassador to Iraq, says Americans on the ground are necessary to win the war.