The Administration has not explained the effect of these withdrawals on other troops deployed for OIF, or the Iraq War, which includes not only U.S. troops located in Iraq but also some 80,000 to 90,000 troops providing theater-wide support in neighboring areas. To identify the implications of troop levels for these and other policy issues, this report 
explains how and why measures of troop levels in five different DOD data sources differ; estimates future troop strength in Afghanistan and Iraq for FY2009-FY2012 under the Obama Administration plan using "Boots on the Ground," the most commonly cited measure; discusses the potential cost implications of these changes in troop levels along with other adjustments; analyzes and explains past trends in troop levels for the Afghan and Iraq Wars under the different measures; and measures contributions and burdens of deployment for the four services. This figure of 294,000 troops is over 100,000 higher than the December 2008 total of 181,000 reported in DOD's oft-cited Boots on the Ground," (BOG) report. Likely Overall Declines: FY2008-FY2012

Based on the plans announced by the Obama Administration described above, CRS estimates that average monthly troop strength in Afghanistan and Iraq will decline from 187,900 in FY2008 to 67,500 in FY2012, a drop of 64%. By showing average troop strength both in the past and estimating troop strength in the future, CRS hopes to provide a tool that can help Congress assess the pacing cost implications in current plans to increase troop levels in Afghanistan and decrease troop levels in Iraq including:
Are the planned increases in Afghanistan too much, too little or about right and how long are higher levels likely to be maintained? Changes in Afghanistan and Iraq

For Afghanistan, troops in-country grew gradually from 5,200 in FY2002 to 20,400 in FY2006. Between FY2006 and FY2008, average strength there jumped by another 10,000 to 30,100. Under the Administration's plans, CRS estimates that average monthly Boots on the Ground in Afghanistan may increase to 50,700 in FY2009 with a further increase to 63,500 the following year once all new units are in-place (see Table 2 ). Currently, additional increases have not been approved. For Iraq, troops in-country nearly doubled between FY2003 and FY2004 reaching an average of 130,600. By the following year, average strength grew by another 13,000 to 143,800, with that level maintained in FY2006. During the surge in troops initiated by President Bush, average troop strength in Iraq initially grew by 7,000 or 6% in FY2007, less than the increase between FY2005 and FY2004. By the next year with another 9,500 troops, troops or another 9%, reaching a peak of 157,800 even as the additional combat brigades began to be withdrawn. CRS estimates that troop strength in Iraq will average 135,600 in FY2009, 88,300 in FY2010, 42,800 in FY1011, and 4,100 in FY2012. For FY2010, the Administration has requested $130 billion in FY2010 for both wars. Because of these transfers, the FY2010 war request would be expected to be $8 billion lower than in FY2009. Based on currently announced plans, CRS estimates that war costs could total $92 billion in FY2011 and $70 billion in FY2012. These levels would be $42 billion and $20 billion, respectively, above the current planning figures. Using this method, average monthly troop strength for both wars in FY2008 ranged from: 188,000 for DOD's Boots on the Ground or troops deployed in Afghanistan and Iraq; 223,000 in the Central Command's Operations Report including some but not all troops deployed in the region, or 19% above the BOG total; 248,000 in average strength estimated from combat pay, or 32% above the BOG total; 294,000 in the Defense Manpower Data Center average strength or 56% above the BOG total; and 307,000 troops based on DMDC's Location Report, or 64% above BOG figures; (see Table 4 ). Before the invasion of Iraq in March 2003, all troops deployed in the theater were allocated to OEF. Changes in troop levels in Iraq appear to be loosely related to changes in military strategy including:
a quick peak for the invasion itself followed by a rapid drawdown; limits on troop strength reflecting the military strategy endorsed by General Abizaid, the commander in-country, to minimize military presence in order to prevent insurgents from using the U.S. occupation as a way to gain popular support; a shift in the U.S. strategy in October 2005 announced by Secretary of State Condoleezza Rice to "clear, hold, and build" so as to "clear areas from insurgent control," that would gradually be implemented as U.S. troops moved out of large bases to work more closely with Iraqi forces; and the surge in troops announced by President Bush in January 2007 that temporarily increased the number of troops by 30,000 and the number of Brigade Combat Teams from 15 to 20 in order to implement the new counter-insurgency policy to help Iraqis clear and secure neighborhoods. It is not clear whether average costs will continue to rise or fall as the number of troops in-country increases. CBO does not distinguish between OEF and OIF.
In February and March 2009, the Obama Administration announced its plans to increase troop levels in Afghanistan and decrease troop levels in Iraq. In Afghanistan, 30,000 more troops are deploying this year while in Iraq, troops will gradually decline to 35,000 to 50,000 by August 31, 2011 with all troops to be out of Iraq by December 31, 2011. The most commonly cited measure of troop strength is "Boots on the Ground" or the number of troops located in Afghanistan and in Iraq. Based on average monthly Boots on the Ground figures, the number of troops in Afghanistan and Iraq increased from 5,200 in FY2002 to a peak of 187,900 in FY2008 primarily because of increases in Iraq beginning with the invasion in March 2003. In FY2009, total troop strength is expected to remain the same as planned increases in Afghanistan offset declines in Iraq. By FY2012, overall troop strength for the two wars is likely to decline to 67,500 when the withdrawal from Iraq is expected to be complete.
For Afghanistan, troops in-country grew gradually from 5,200 in FY2002 to 20,400 in FY2006. Between FY2006 and FY2008, average strength there jumped by another 10,000 to 30,100. Under the Administration's plans, CRS estimates that average monthly Boots on the Ground in Afghanistan may increase to 50,700 in FY2009 with a further increase to 63,500 the following year once all new units are in place. Currently, additional increases have not been approved.
For Iraq, troops in-country nearly doubled between FY2003 and FY2004 reaching 130,600. By the following year, average strength grew by another 13,000 to 143,800, with that level maintained in FY2006. During the surge in troops initiated by President Bush, average troop strength in Iraq grew by 7,000 or 6% in FY2007 and another 9,500 or 9% in FY2008, reaching a peak of 157,800. CRS estimates that average troop strength in Iraq will decline to 135,600 in FY2009, 88,300 in FY2010, 42,800 in FY2011, and 4,100 in FY2012. While it is not clear whether war costs will change precisely in tandem with troop levels, these changes can provide a benchmark to assess requests. Based on changes in troop levels and other adjustments, CRS estimates that war costs could be about $8 billion less than the Department of Defense (DOD) $141 billion request for FY2009, and about $13 billion below its $130 billion request for FY2010. For the next year, FY2011, CRS estimates that DOD's requests could be $42 billion more than the current planning figure of $50 billion. And in FY2012, CRS estimates war costs could be $20 billion higher than the Administration's estimate of $50 billion.
Although Boots on the Ground is the most commonly cited measure of troop strength, that measure does not include over 100,000 other troops deployed in the region providing theater-wide support for Operation Enduring Freedom (OEF), the Afghan War, and Operation Iraqi Freedom (OIF), the Iraq War. Before the 9/11 attacks, the United States had deployed about 26,000 troops in the Central Command region, which includes Afghanistan and Iraq. Based on the most comprehensive DOD measure of troop strength, 294,000 troops were deployed for OEF and OIF as of December 2008, a tenfold increase since 2001.This more inclusive measure may more accurately capture the overall demand for troops. The Administration has not indicated how its plans would affect troops providing support in the region. Using five DOD sources, this report describes, analyzes, and estimates the number of troops deployed for each war from the 9/11 attacks to FY2012 to help Congress assess upcoming DOD war funding requests as well as the implications for the long-term U.S. presence in the region.