With Petraeus giving pivotal testimony to lawmakers in Congress on President George W. Bush's war strategy deploying additional troops, the following are key facts related to US troop deployments in Iraq:

-- Peak "surge" strength is 20 combat brigades or about 160,000 troops, although current force level is 168,000 troops due to overlapping unit rotations.

-- A Marine Expeditionary Unit, about 2,000 troops, departs Iraq later this month.

-- An army combat brigade, or about 4,000 troops, redeploys in December and is not replaced.

-- Four army combat brigades and two marine battalions return home by July 2008, reducing US forces to pre-surge levels of 15 combat brigades.

-- There were 130,000 troops in Iraq before the surge, but Petraeus said military police and other support units that were added during the surge will stay.

-- No later than March, Petraeus will make recommendations on further reductions and mission changes after July 2008.

related report
US occupation of Iraq in numbers
Following are vital statistics on the occupation of Iraq, nearly four and a half years after the US-led invasion:

US military dead: 3,759

US wounded in action: 27,767

Iraqi civilians killed: Estimates range widely from 70,000 to 150,000. A controversial US study last year estimated as many as 655,000 Iraqis have died of war-related causes.

Total US troops: 168,000

Total Iraqi security forces: 360,000

Cost: 450 billion dollars, according to the Congressional Research Service. Iraq war cost are estimated 165.8 billion dollars in fiscal 2007, up 40 percent over the previous year, or about 12 billion dollars a month.