Troop Levels in Stability Operations: What We Don't Know

By Peter J.P. Krause, MIT Center for International Studies. Posted March 26, 2007.

Troop levels in Iraq have been one of the most hotly contested issues in American foreign policy over the past three years, from debates over the initial deployment in 2003 to those surrounding the troop surge in 2007. The Bush administration has faced significant criticism for ignoring the conventional wisdom regarding the number of soldiers required to secure Iraq, and recent attempts to change course in this area are seen by some as too little, too late.

Specifically, the Pentagon's deployment of only 120,000 American troops for the invasion and the decision by Paul Bremer, U.S. Administrator in Iraq, to disband the Iraqi army and police has kept the ratio of security forces to Iraqi civilians well below the 20 per 1,000 seen as the basic ante required to play the high stakes stabilization game. Many supporters of higher troop levels blame these missteps for the emergence of the robust insurgency and the coalition's failure to defeat it.

But where exactly does the 20 per 1,000 figure come from, how strong is the evidence supporting it, and what steps are being taken to assess and improve the conventional wisdom in this area? While the answer to the first part of the question is relatively accessible, the latter are more difficult. They address a daunting problem, but unveil a disconnect between the objectives and methods of policy and social science.

Troops Levels and Iraq

Army Chief of Staff Eric Shinseki set off a firestorm when he told the Senate Armed Services committee before the invasion that "something on the order of several hundred thousand soldiers" would be required to stabilize Iraq, a figure that began to approach 20 troops per 1,000 of the Iraqi population, the ratio that academics conventionally, if not universally, cite as necessary for successful stability operations. Secretary of Defense Donald Rumsfeld called this estimate "far off the mark," as did Deputy Secretary Paul Wolfowitz, who put the figure closer to 100,000 troops total for Iraq. As the war drags on, requiring orders of magnitude greater time, blood, and treasure than estimated by U.S. leadership, troop figures have become the foremost issue debated at all levels.

The debate over troop levels has been constant throughout the war, even among military leaders; a growing number of Democrats and Republicans in Congress are pushing to decrease troop levels over a varying set of timetables. However, President Bush has opted for an increase in troop levels over the coming months as part of one final push to achieve the "victory" he sees as the only acceptable option.

There are currently 169,000 coalition troops (including 152,000 Americans) deployed to Iraq, a ratio of 6.3 per 1,000 if only these forces are counted. If the Iraqi army is added into the mix, then the figure becomes 11.3 per 1,000, and 18.4 per 1,000 if Iraqi police forces are also included. The addition of approximately 20,000 U.S. troops would push those ratios to 7.1, 12.1, and 19.1 per thousand, respectively. These figures include non-combat support troops as well as all Iraqi army and police units that are "in the fight" according to CENTCOM, regardless of readiness. When "tooth-to-tail" considerations are included-the number of combat troops to logistical support troops-the number of U.S. combat troops in country drops to about 60,000, and coalition and Iraqi force figures face similar reductions. Therefore, only if these best case figures are used with all support troops and all Iraqi police included does the current figure even begin to approach the 20 per 1,000 believed to be needed for success.

Glass Half Empty?

Scholarship has less to offer than it should for an issue -- the stabilization of a country by security forces -- that has formed a key part of every military intervention abroad as well as the actions of every state within its own borders on a daily basis. The most well-known and methodologically rigorous work on the topic remains James Quinlivan's "Force Requirements in Stability Operations," now more than ten years old. Quinlivan's article represents an initial attempt to apply the methods of social science to the policy-relevant issue of troop levels. By examining a number of historical cases of stability operations, Quinlivan is able to calculate the troop levels employed relative to the populations they were attempting to control, offering a basic method for calculating the ratio required for successful stabilization, which he defined as "[creating] an environment orderly enough that most routine civil functions could be carried out." In a revision of the counterinsurgency (COIN) literature, which previously included ratios relative to the number of insurgents or a desired threshold of 10 troops per 1,000 of the population, Quinlivan argues for a ratio of 20 troops per 1,000 of the population to achieve successful stabilization, a figure that has remained largely unchallenged.

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"Peter Krause is a doctoral candidate in political science at MIT and a member of MIT's Security Studies Program."