Twenty years ago, the United States invaded Iraq and unwittingly ushered in a lengthy struggle for stability and security in the country. U.S. President George W. Bush and Secretary of Defense Donald Rumsfeld expected a short, sharp war that would end once U.S. forces expelled the Iraqi dictator Saddam Hussein. The U.S. military was primed to rapidly and surgically cut through the Iraqi army with its high-tech forces, a swift intervention that would culminate in the seizing of Baghdad. Instead, faulty assumptions, mistakes after Saddam’s ouster, and an invasion force that was too small to secure the country allowed the growth of a virulent insurgency that proved difficult to defeat.

Following the initial invasion, the U.S. military found itself embroiled in combat that resembled its fighting in Vietnam in the 1960s and 1970s. But several decades after that war, many of the lessons learned in Vietnam—at such great cost—had been forgotten. After the United States pulled out of Vietnam in 1973, the U.S. military shifted its focus to the threat from the Soviet Union. It stopped teaching its troops how to combat insurgencies, and those capabilities began to atrophy. As a result, it took the U.S. military several years to work out the best way to fight in Iraq. Today, the United States has once again prioritized great-power competition. But it should not make the same mistake of turning its back on preparing to fight insurgencies. The armed forces must be ready for the range of conflicts that may arise in the coming century, and counterinsurgency will surely be in the mix.


During the Vietnam War, the U.S. Army battled both regular North Vietnamese units and Vietcong guerrillas. By the time U.S. forces withdrew from the conflict, they had learned a great deal about counterinsurgency warfare, stability operations, and nation-building. In subsequent years, the army let that experience wane, with what little expertise that remained concentrated at the U.S. Army John F. Kennedy Special Warfare Center. The bulk of the armed forces turned instead to preparation for high-intensity combat against Warsaw Pact forces in Europe.

The collapse of the Soviet Union in 1991 set the U.S. military adrift. Great-power conflict was unlikely for the foreseeable future, and military leaders struggled to define their mission and determine how best to organize their forces. Some policymakers embraced the use of the armed forces for small-scale contingencies, peacekeeping operations, and “military operations other than war,” a phrase popular among policymakers in the 1990s. Secretary of State Madeleine Albright was among them, famously quipping to Colin Powell, then chairman of the Joint Chiefs of Staff, “What’s the point of having this superb military you’re always talking about if we can’t use it?” Indeed, in the 1990s, Washington deployed the military to Somalia, Haiti, Bosnia, and Kosovo. These operations enabled the distribution of food aid, forced a dictator from power, helped stop a civil war, and ultimately birthed a new country, but they did not come without cost. The American public was quick to question the goals of U.S. military deployments once they incurred casualties.

Despite these largely successful small deployments, U.S. military leaders remained wedded to planning for large-scale combat operations. U.S. Navy admirals and Air Force generals viewed a rising China as the next great threat. Army trainers continued to pit combat teams at the National Training Center against an opposing force that looked suspiciously like the Soviet army in desert camouflage. The U.S. Joint Forces Command went further, training for operations against imaginary enemies akin to the United States—mirror-imaged adversaries that did not exist in the real world. The armed forces bought into a revolution in military affairs, using new technology, doctrine, and organizations that coupled guided munitions with cutting-edge intelligence, surveillance, and reconnaissance systems that would theoretically dispel the fog of war, reduce friction on the battlefield, and enable victory in future wars at a low cost. Wars against great-power adversaries and less powerful states such as Iran, Iraq, and North Korea would be quick, inexpensive, and decisive.

For a brief moment after the invasions of Afghanistan and Iraq, it appeared that the theorists were right. In both countries, regime change was accomplished quickly and with limited expenditure of blood and treasure. But little thought had been put into what would follow, and the resulting occupations turned into messy nation-building affairs for which the U.S. Army and Marine Corps were ill prepared. Destroying the Iraqi armed forces and the Taliban was far easier than installing new governments and stabilizing countries that had been traumatized by years of misrule. As the U.S. military faltered, virulent insurgencies erupted, supported by neighboring states with agendas that ran counter to American interests.


For several years, operations in Iraq floundered as military leaders came to grips with the type of war they had to fight. Commanders were initially encouraged to conduct offensive operations against both jihadi terrorists and stubborn holdouts from Saddam’s regime, whatever the costs for the Iraqi people. General John Abizaid, then the head of U.S. Central Command, worried that U.S. and other foreign forces were “antibodies” that would create more insurgents than they would suppress. He ordered U.S. forces to pull out of Iraqi cities to limit the provocations that could stoke resentment and stir further violence. But since the new Iraqi army and police lacked personnel and were not yet ready, that withdrawal allowed Sunni insurgents and Shiite militias to take over neighborhoods. Sectarian tensions erupted when al Qaeda terrorists bombed the al-Askari shrine, a Shiite holy site in Samarra, in February 2006, leading to a civil war that threatened to tear Iraq apart.

Even as senior commanders remained wedded to existing strategic and operational concepts, midlevel leaders such as Colonel H. R. McMaster, Lieutenant Colonel Dale Alford, and Colonel Sean MacFarland experimented with counterinsurgency operations in Tal Afar, al-Qaim, and Ramadi. They positioned their forces in smaller outposts in urban areas and allied with local tribes and leaders to oppose al Qaeda and other insurgent groups. In December 2006, the U.S. Army Combined Arms Center and the Marine Corps Combat Development Command jointly published a new counterinsurgency manual that focused on protecting the local population from insurgent intimidation and violence as the key to success. In addition, Bush revamped the military’s leadership, dismissing Rumsfeld and his battlefield commander, General George Casey, and replacing them with Bob Gates and General David Petraeus, who were determined to prosecute a robust counterinsurgency campaign to improve the coalition’s fortunes in Iraq. Bush provided them with the resources to do so during the troop surge of 2007–8, going all in to defeat al Qaeda in Iraq and stabilize the country.

Destroying armies is far easier than installing new governments.

Aided by the Sunni Awakening, a U.S.-backed tribal revolt against al Qaeda in Anbar Province, the surge succeeded beyond all expectations. The United States changed its objective from creating a Jeffersonian democracy to the more manageable goal of “sustainable stability,” providing a safe environment in Iraq that would create the conditions for democracy in the long term. U.S. forces shifted their focus to conducting counterinsurgency operations centered on securing Baghdad and the belts of territory surrounding it and destroying al Qaeda in Iraq. By this point, U.S. troops—many with multiple tours under their belts—had learned new counterinsurgency tactics, techniques, and procedures at the sharp end of combat. The ranks of the Iraqi security forces swelled as well, growing to more than 350,000 soldiers and police officers, with U.S. advisers now embedded in most formations. And more than 100,000 local citizens, the so-called Sons of Iraq, stepped forward to guard their communities against the depredations of terrorists, insurgents, and Shiite militias alike.

By the end of the surge in the summer of 2008, security incidents in Iraq had declined by more than 90 percent from pre-surge levels. This relative calm enabled successful elections in 2009 and 2010, which backfired when Iraqi Prime Minister Nouri al-Maliki, who had been defeated at the polls in the latter election and was in danger of being turned out of office, retaliated by targeting his political enemies, rekindling the fires of civil war. Maliki and the administration of U.S. President Barack Obama could not agree on renewing the agreement that governed the conduct of American forces in Iraq, leading to the withdrawal of U.S. troops at the end of 2011. Without the tutelage of U.S. advisers, the Iraqi security forces began to deteriorate as Maliki removed competent commanders and allowed corruption to hollow out the army.  

After the Islamic State of Iraq and Syria (also known as ISIS) invaded Iraq in 2014, U.S. forces returned, this time in a supporting role to the Iraqi Army and the Syrian Democratic Forces, a Kurdish-led militia. The proxy fight against ISIS worked well. Backed by robust airpower, limited numbers of U.S. Special Forces, ground troops, and advisers teamed up with Iraqi and SDF forces to crush ISIS.


Conflicts do not end with the destruction of an adversary’s armed forces. Through years of trial and error in Iraq, the U.S. military figured out ways to secure and control local populations, conduct precision counterterrorist operations, create effective local security forces, gather intelligence, prevent disinformation from spreading, engage neighboring states to eliminate sanctuaries for insurgents, stabilize the local economy, and set up effective governments—so-called nation-building operations.

With the “global war on terror” now in the rearview mirror, the U.S. military is no longer rigorously training its soldiers and officers in the prosecution of counterinsurgency warfare. The U.S. military has closed its Counterinsurgency Center, reduced the number of hours devoted to counterinsurgency training in professional military educational institutions, and stopped counterinsurgency training at its combat training centers.

After the Vietnam War, the U.S. Army did its best to forget the lessons of counterinsurgency. Counterinsurgency and low-intensity conflict all but disappeared from the curriculum of professional military education. From the mid-1970s until the September 11 attacks in 2001, the army assumed that most of its soldiers, save for a small number of special forces, could ignore counterinsurgency warfare. With the defeat of ISIS and the withdrawal of U.S. forces from Afghanistan, the likelihood of counterinsurgency disappearing from U.S. military education and training was already high. The invasion of Ukraine and the potential return of great-power conflict makes it all but certain.

The U.S. military is not wrong to focus today on potential conflicts with China, Iran, North Korea, and Russia—the United States’ most dangerous enemies. But U.S. military leaders should not ignore the equally likely scenario that they will need to fight small-scale battles against shadowy organizations. If officers and senior noncommissioned officers are educated for the full gamut of threats the country might face in the years ahead, including counterinsurgency warfare, the soldiers they lead can quickly adapt to situations on the ground. Keeping counterinsurgency and small-scale warfare curricula in command and general staff courses and war colleges is a small price to pay to prevent a rude shock in the future. But it would be a tragedy if senior U.S. military leaders, like their late Cold War counterparts in the post-Vietnam years, decided to jettison lessons learned the hard way in Iraq by assuming the United States will never fight that kind of war again. U.S. military history suggests otherwise.

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  • PETER R. MANSOOR, a retired Colonel in the U.S. Army, is Raymond E. Mason, Jr., Chair in Military History at the Ohio State University. He served as a Brigade Commander in Iraq in 2003–4 and as Executive Officer to General David Petraeus, Commander of the Multinational Force–Iraq, in 2007–8.

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