Ever since World War II, the United States has depended on armored forces -- forces equipped with tanks and other protected vehicles -- to wage its wars. General Omar Bradley, the senior field commander of the U.S. ground forces that conquered Nazi Germany, noted in his official after-action report that tank warfare, especially when combined with airpower, proved essential in defeating the Wehrmacht. "The air-armor team is a most powerful combination in the breakthrough and in exploitation," he wrote, adding, "the use of this coordinated force, in combat, should be habitual." In the decades that followed, the U.S. military frequently employed armored forces, relying on them during the Korean War, the Vietnam War, the Gulf War, the Afghan war, and the Iraq war.

Organized into units called "armored brigade combat teams," which consist of about 4,500 soldiers outfitted with Abrams tanks and Bradley Fighting Vehicles, the U.S. Army's armored forces are among the most expensive ground formations to train and equip. They require more time to deploy and a considerable amount of resources to sustain. Yet they have been invaluable on the battlefield. Thanks to their speed, protection, and firepower, along with their ability to work in concert with many other types of ground forces, armored forces have played crucial roles in defeating enemy militaries, toppling hostile regimes, fighting insurgents, and establishing security. Their ability to keep pace with fast-moving aircraft has made them particularly useful when operating as part of an air-ground team. Against enemies concentrated or dispersed, they have delivered rapid, successive blows, turning tactical gains into strategic successes.

Despite their utility, however, some critics have begun to question the value of armored forces. They argue that the United States' "pivot" to Asia relies more on naval and air forces and that the use of NATO airpower in Libya foretells a future way of war that has little need for ground forces, particularly armored ones. Meanwhile, looming budgetary constraints, along with the army's ongoing downsizing after Afghanistan and Iraq, have enhanced the appeal of lighter, smaller, and cheaper forces.

But armored forces are an essential part of a capable U.S. military. Not only have their unique qualities served the United States well in past wars; those features will also prove necessary for fighting the wide range of military operations the country is likely to take on in the future. In a 2011 document outlining U.S. defense strategy, the Joint Chiefs of Staff stated that the military exists to "prevent attacks against the United States and its allies, strengthen international and regional security, and be prepared to deter and defeat aggression." If the United States fails to maintain an adequate armored combat capability, it would be hard-pressed to fulfill those vital national security goals. And U.S. Army soldiers would face much greater risks.

STATES ON STATES

One of the United States global roles is to deter adversaries from committing acts of aggression. In large measure, deterrence rests on the ability to defeat the militaries and proxy forces of hostile states. Because they are well suited to seizing terrain and exercising control over populations and resources, armored forces are critical both to deterring aggression and to winning conflicts when deterrence fails.

That value was apparent during the 1990-91 Gulf War. To expel Saddam Hussein's forces from Kuwait and eliminate their capability for further aggression, the United States and its coalition partners employed a ground force that included six armored divisions, two armored cavalry regiments, and a separate armored brigade, all of which were equipped with tanks, mechanized infantry units, and attack helicopters. Even though the United States completely dominated the air and the sea, it still relied on armored forces to defeat Iraq's Republican Guard. After the conflict, Washington demonstrated its continued commitment by stationing large numbers of armored ground forces next door in Kuwait, which continue to reassure U.S. allies in the region and deter aggression to this day.

When the United States invaded Iraq in 2003, it again relied heavily on armored forces. Military planners had expected U.S. forces to make contact quickly with Iraqi forces, but in the offensive push to Baghdad, Saddam's military proved elusive. Units assigned to the U.S. Army's V Corps, the main force invading Iraq, discovered that almost every mission was a "movement to contact," meaning that soldiers found themselves encountering both conventional and unconventional forces at unexpected times and places. As a result, they had to fight for information and quickly develop their own understanding of the situation in battle.

Even large Iraqi units were able to achieve surprise. When the Third Infantry Division crossed the Euphrates River, for example, an undetected Iraqi armored brigade launched a sudden counterattack. In this chaotic environment, the division's armored forces possessed enough protection to bear the brunt of the enemy attack, enough mobility to maneuver to advantageous positions, and enough firepower to overwhelm the enemy while taking very few casualties. Within weeks, U.S. forces took Baghdad and Saddam's regime fell.

The United States is not the only country that recognizes the value of armored forces, which is another reason it needs to retain enough of its own. When Russia invaded Georgia in 2008, its ground forces, including armored units, took just a few days to crush the five or so Georgian brigades that had been trained by the United States. This and other episodes of armored warfare, such as Syria's use of tanks against its own population, highlight the need for the United States and its allies to retain sufficient armored forces to deter and, if necessary, confront large, well-armed ground forces.

Meanwhile, a number of militaries in the Middle East and East Asia -- namely, those of Iran, Syria, China, and North Korea -- also possess capable armored forces. These militaries have studied how to mitigate advanced airpower and surveillance capabilities, such as those possessed by the United States and its NATO allies. To deter these states, the United States needs a balanced force able to overcome their countermeasures -- and armored brigade combat teams are a fundamental component of that balanced force. At a time when the North Korean dictator Kim Jong Un has announced the abrogation of the Korean War cease-fire, for example, armored forces already on the Korean Peninsula, as well as those stationed nearby, have remained crucial to protecting U.S. allies and interests in Asia.

U.S. armored forces also play a critical role in building capacity among friendly and allied states. Around the globe, the U.S. military advises foreign forces to help promote regional stability. Many of these militaries field large armored forces of their own, and training them how best to employ such forces requires expertise and sufficient numbers of trained personnel. Perhaps the best example is the ongoing training mission in Saudi Arabia, where the U.S. Army has provided advice and assistance to the Saudi Arabian National Guard's military schools, brigades, and headquarters for the past 39 years.

COUNTERING INSURGENTS

The wars in Afghanistan and Iraq demonstrated how important it is for the U.S. military to be able to fight not only traditional militaries but also nonstate organizations. Counterinsurgency campaigns usually evoke images of infantry squads patrolling neighborhoods on foot, but they also require tanks and armored vehicles. Protected inside armored vehicles and armed with precise firepower, soldiers can take greater risks to secure the population, holding fire until the enemy reveals its hostile intent.

The U.S. Army used tanks and armored units to great effect in Iraq, and the U.S. Marine Corps, along with forces from Canada, Denmark, and Germany, did the same in Afghanistan. It may seem somewhat counterintuitive, but the firepower provided by Abrams tanks (each armed with a large cannon and a heavy machine gun) and Bradley Fighting Vehicles (each armed with a chain gun and an antitank missile launcher) is highly discriminate. These weapons inflict less collateral damage than artillery, mortars, or air strikes, and they enable U.S. forces to overwhelm the enemy even as they protect innocents.

Moreover, unlike any other type of force, armored brigade combat teams have the versatility to scale down for low-level adversaries or scale up against more lethal enemies, even in the midst of an irregular conflict. In Iraq, during the fight for Sadr City in 2008, units that had been patrolling Baghdad in lightly armored wheeled vehicles quickly replaced them with tracked Abrams tanks and Bradley Fighting Vehicles as the violence escalated, and then returned to their wheeled vehicles after the battle. Light infantry units have no comparable ability; they can contend with more lethal adversaries only if complemented by armored forces.

The fight for Sadr City represents just one of many operations in which armored forces proved their mettle in Iraq. During battles in Karbala, Baghdad, Fallujah, Najaf, Tal Afar, Diwaniyah, and Baqubah, armored units outmatched the insurgents, protected lighter forces, and were able to maneuver through roadblocks, improvised explosive devices, and other obstacles.

The Battle of Karbala, in April 2003, is a particularly powerful case study of their value. Light infantry units of the army's 101st Airborne Division were charged with clearing Saddam's military and paramilitary forces from the city, but they immediately met stiff resistance from militiamen on rooftops firing machine guns and rocket-propelled grenades. The American foot soldiers, armed only with machine guns and light antitank weapons, found themselves unable to advance.

Until supporting armored units rolled in with their Abrams tanks and Bradleys, that is. Working as a team, the infantry and the armored units overwhelmed enemy defenses at the fringes of Karbala and allowed the light infantry to begin systematically clearing the dense city. Because every armored vehicle was outfitted with capable communications equipment, they were also able to direct close air support and precise artillery and mortar fire. Armored vehicles breached 12-foot walls and other barriers with ease. As the light forces cleared house after house, their comrades in armored vehicles protected them, established roadblocks, and ensured communications between mounted and dismounted forces. Were it not for the unique capabilities of its armored forces, the U.S. military would have paid a heavy price in Karbala.

Yet another lesson of the Iraq war is that armored forces need to be used in sufficient scale. The invading coalition had enough ground forces to topple Saddam's regime, but not enough to consolidate its gains and establish security. As a result, a nascent insurgency coalesced and gained strength. As the U.S. military fought to turn the tide, it learned that large numbers of armored forces were needed to establish security over wide areas.

The Israelis learned the same lesson in their 2006 campaign against Hezbollah in Lebanon. That summer, some 3,000 to 4,000 Hezbollah fighters concealed themselves in complex terrain that measured only 30 miles deep and, at its widest point, 30 miles across. To stop Hezbollah from launching rockets into Israel, the Israel Defense Forces needed to establish security over the entire area. But the IDF, trained to conduct raids in low-intensity conflicts, was never able to do so, even though it employed elements of at least four divisions, including 12 brigades and other reserve forces -- a total of almost 30,000 soldiers.

The main problem was Israel's inability to employ its armored formations in close cooperation with infantry and other units. Had the IDF been able to do so, it could have used its armored forces to fight through long-range weapons fire and overwhelm the enemy through surprise, speed, and firepower. That, in turn, would have allowed them to preserve their forces' freedom of maneuver and safely get light and medium forces close to the fight. Indeed, Israel learned its lessons, changing tactics during the Gaza operations in 2009 and 2012 to great effect.

ARMORING AGAINST UNCERTAINTY

When determining what role armored forces should play in the U.S. military, decision-makers should consider not only how they have contributed to victory in the past but also how they will be needed in the future. The adversaries the United States is most likely to face in the next decade are already gaining new capabilities and taking advantage of a rapidly changing operational environment. Countering them will require a wide range of capabilities, some of which only armored forces can provide.

Some defense analysts have argued that the best way to cope with sophisticated threats is through the application of precise firepower from the air and the sea. But the United States' adversaries are well aware of its impressive surveillance and precision-strike capabilities and are already devising tactical countermeasures to defeat them. They have made plans for dispersing forces and concealing them among local populations, and they are developing technologies that will offset U.S. advantages, such as man-portable air defense systems, antitank guided munitions, and surface-to-surface rockets. Defeating elusive adversaries equipped with such weapons will require sufficient armored forces, which have the protection, mobility, and firepower to seek out and destroy enemies on the ground.

In addition to high-end threats from states and low-end threats from irregular forces, the United States must also be prepared to deal with a third type of challenge: so-called hybrid adversaries. These state-sponsored opponents are small in number, moderately trained, and often decentralized, but what they lack in manpower they make up for in firepower. Hezbollah, for example, now possesses mortars, rocket-propelled grenades, antitank guided missiles, long-range rockets, man-portable air defense systems, and even unmanned aerial vehicles. Hybrid adversaries can also attack U.S. forces by resorting to cyberwarfare, GPS jammers, and improvised explosive devices. The most effective way to defeat such organizations is by establishing control over territory and the people living there -- a kind of mission that cannot be accomplished without armored forces.

As military technologies continue to spread, all three types of adversaries -- states, nonstate actors, and hybrid entities -- will employ advanced weapons to deny U.S. forces the ability to operate in protected areas. To address this challenge, the military will need armored forces to fight their way through long-range weapons fire and gain physical contact with hard-to-find opponents. Tanks and armored vehicles can maneuver quickly to strike the enemy from unexpected directions with multiple forms of firepower at a range of two to three miles. With the right training, organization, and equipment, armored forces can survive and succeed in the face of highly capable enemies.

A FORCE FOR THE FUTURE

At a time when budget constraints are forcing the Pentagon to make tough choices, the army's armored forces may seem like an extravagance. And at a time when precision-guided missiles can destroy faraway targets in seconds, tanks and armored vehicles might appear obsolete. To some, armored forces look like a hulking, overpriced holdover from a bygone era.

Nothing could be further from the truth. The U.S. military's armored forces have played a vital role in deterring aggression, toppling regimes, and defeating conventional forces and insurgents alike. And they will become even more important as potential adversaries continue to adapt to the U.S. military's advantages in airpower, sea power, surveillance, and targeting. Operating alongside the army's light and medium forces, armored brigade combat teams possess the protection, mobility, and firepower needed to defeat capable state and state-sponsored enemies. Only armored brigade combat teams, moreover, have the versatility to scale down for irregular conflict and other campaigns such as peacekeeping operations, humanitarian interventions, and missions to train foreign militaries. In these and so many other ways, they act as the United States' hedge against an uncertain future.

Decisions about the U.S. Army's force structure and capabilities are complicated and rarely discussed outside the Pentagon. But they matter greatly: once taken, they will shape the military options available to the president and affect the Pentagon's ability to execute defense strategy for years to come. As the country considers how to shape the military of tomorrow, it should be wary of forfeiting the power and flexibility provided by sufficient numbers of trained and ready armored forces. Were they abandoned, such capabilities would be extremely hard to regenerate.