Spurred by a continued decline in violence, the U.S. military will reduce its presence in Iraq from 16 combat brigades to 14 this month, at least two months earlier than planned.

Military officials say two brigades from the 101st Airborne Division will leave Iraq this month, and only one will be replaced. A brigade is roughly 3,500 soldiers. Initially the 3rd Brigade, 101st Division, was scheduled to leave this month, and the 2nd Brigade, 101st Division, was to leave by February.

On Wednesday, the military announced the 2nd Brigade will instead return this month to its home base, Fort Campbell, Kentucky, after serving 13 months in Iraq rather than the expected 15.

The unit served in northwest Baghdad, where violence has plunged, including a 50 percent decline in overall attacks in the area and a more than 90 percent drop in murders.

U.S. forces also have seen a dramatic decline in troop fatalities, with deaths falling to their second lowest monthly level in October. Fourteen U.S. troops killed last month, including seven in combat. That total was one more than the 13 deaths in July, the lowest monthly level of the war.

President George W. Bush announced in September that the military would go from 15 to 14 combat brigades in Iraq some time in January on the recommendation of Gen. David Petraeus, then his top Iraq commander.

The decision sparked sharp criticism from Congress members who wanted Petraeus to recommend a swifter and larger drawdown in Iraq. The plan appeared to push decisions for any more aggressive troop cutbacks to the next administration.

The congressional opponents complained that the decision made it more difficult to divert additional forces to Afghanistan, where commanders have asked repeatedly for thousands more troops.

At the time, however, Defense Secretary Robert Gates urged a cautious approach in Iraq, saying commanders did not yet believe the security gains were "enduring," and there was the potential for reversals in the future.

More recently, however, Gates and other officials have talked more insistently about the need to boost troop levels in Afghanistan, noting that the increase cannot take place until more forces come home from Iraq.

President-elect Barack Obama has said he wants to withdraw combat troops from Iraq in 16 months, and he has recommended increased U.S. forces in Afghanistan.