Earlier this month, the Modern War Institute published an opinion piece, “The Tyranny of Battle Drill 6,” by retired Colonel Richard Hooker. In the article, Hooker argues that due to a culture of specialized urban tactics, conventional infantry soldiers should completely stop training to clear rooms. This is a dangerous position, one that skips over most of the context surrounding why the US Army prepares close-combat formations for urban warfare. In fact, the Army should be doing more to train its conventional infantry units for urban environments—including clearing rooms—not less.

Without Question, Infantry Will Have to Keep Clearing Rooms

The idea that infantry soldiers should stop training to clear rooms is just not informed by global trends, the Army’s history, or the character of modern warfare.

The world is urbanizing at unprecedented speed and scale. In 1970, only 1.3 billion of the world’s 3.7 billion people were urban dwellers. By 2020, over 4.3 billion (56 percent) of the global population of 7.7 billion were living in urban areas. The UN estimates that by 2050 two-thirds of the world will be urbanized. Across Western Europe, the Americas, Australia, Japan, and the Middle East today, more than 80 percent of the population lives in urban areas. Rapid urbanization, globalization, the fall of super- and regional powers, and resource scarcity have all contributed to turning political violence, intrastate war, and conflict in general into an urban-dominated phenomenon. The era of urban warfare is already here.

Cities are the economic and political centers of gravity for nations and historically have been the culminating sites of state-on-state, peer warfare. Both state-sponsored and nonstate actors see fighting in urban terrain and embedding within civilian populations as an effective countermeasure against Western maneuver, fires, and intelligence, surveillance, and reconnaissance capabilities. The need for Army formations to close with and destroy enemy forces in buildings and rooms in support of the service’s mission statement—“defeating enemy ground forces and indefinitely seizing and controlling those things an adversary prizes most—its land, its resources and its population”—will only grow.

A Brief History of Room-Clearing Tactics and Battle Drill 6

The starting point of Hooker’s opposition is a video that went viral on social media in February 2021. The video shows soldiers of the 10th Mountain Division incorrectly conducting the infantry Battle Drill 6—“Enter and Clear a Room.” Despite Hooker’s argument against conventional infantry soldiers conducting room clearing, the soldiers in the video were not actually infantry soldiers. That might seem like a minor detail, but it becomes important when we examine the history and evolution of training on room clearing (using close-quarters battle tactics) done by the Army in the modern era.

Most urban warfare scholars attribute the beginnings of close-quarters battle (CQB, also sometimes called close-quarters combat) tactics to the failed raid to save Israeli Olympians in Munich in 1972. As Hooker notes, the CQB tactics developed and refined by counterterrorist units such as Special Forces Operational Detachment–Delta (SFOD-D) did pass into other special operations forces and eventually into conventional military units, both in the United States and around the world. What people often get wrong is that CQB is not the start of the US Army’s room-clearing tactics.

The US Army has a long history of doctrine reflecting its experience in urban environments. Sections of doctrine on urban warfare, to include tactics for use specifically in villages and towns, pre-date World War II, but post–World War II Army manuals are the ones that first start to codify room-clearing tactics. The Army had learned valuable lessons from its experiences in major World War II battles such as Aachen and Manila and in later city fights like Seoul during the Korean War and Hue in Vietnam.

In 1979, one of the Army’s first urban warfare–specific manuals—Field Manual (FM) 90-10, Military Operations on Urbanized Terrain (MOUT)—described “how to attack and clear buildings” and is one of the Army’s first documented attempts to formalize tactics for room clearing using the lessons learned during and after World War II. The instructions were simple: Step 1, shoot door open. Step 2, toss grenade. Step 3, enter firing and search room.

Image source: FM 90-10, Military Operations on Urbanized Terrain (MOUT) (1979)

In 1982, FM 90-10 subsequently spawned FM 90-10-1, An Infantryman’s Guide to Urban Combat, which had a section on how to conduct room clearing. It required an assault team of at least two soldiers. One would cook off a grenade and then throw it into the room. After detonation, one of the soldiers quickly entered and moved out of the doorway to one side or the other, sprayed the room with automatic fire, and then took up a position where he could observe the entire room while the other team member entered. A subsequent version of the manual issued in 1992—FM 90-10-1, An Infantryman’s Guide to Combat in Built-Up Areas—described room clearing more deliberately with commands like “next man in, left” (or right). The tactic still recommended a two-man team.

One of the first appearances of battle drills (they were previously called common patrolling tasks) was in the 1992 FM 7-8, Infantry Rifle Platoon and Squad, which included Battle Drill 6, “Enter Building/Clear Room.” The drill called for large amounts of suppressive fire from the squad approaching the building, followed by, again, a two-man team (now specified to be the squad leader and team leader), one on either side of the door, throwing a grenade in and then entering. One soldier would go left, the other right, but now doctrine specified that the soldiers should only engage identified or suspected enemy.

There is one other document in which infantry battle drills, urban warfare content, and room-clearing tactics can be found—the US Army Ranger School Handbook (a book produced for Ranger School students, but which heavily influences both Ranger and conventional infantry units). The 1992 Ranger Handbook listed and described Battle Drill 6 in the same way that it appeared in FM 7-8. The 2000 Ranger Handbook did not include Battle Drill 6, but it did include a new chapter on close-quarters combat, which included the use of the “four-man stack” technique to clear rooms—an important change from the previous doctrinal guidance that room clearing should be done with only two soldiers.

In 2003, the Army introduced “Warrior Tasks and Battle Drills” that it wanted all soldiers deploying to Iraq or Afghanistan to train. “Enter and Clear a Room” quickly became required for all soldiers. This may seem odd but based on the nature of combat in Iraq and Afghanistan, it was not just infantry soldiers that were conducting missions requiring room clearing. It was regular practice for non-infantry units—armor, cavalry, engineers, and others—to be given ownership of battlespace, requiring them to conduct urban operations, especially raids on insurgent or terrorist targets. One of the most frequent offensive missions soldiers were conducting were intelligence-driven raids on targeted individuals in mostly permissive and often urban environments (meaning situations where the entire urban area was not hostile and the unit had identified the known or likely enemy position) where the enemy was intermixed with civilians. The Army’s tactics matched its requirements in counterterrorism and counterinsurgency operations.

In the next update of FM 7-8, which came in 2007 and renamed the manual FM 3-21.8, all infantry battle drills were removed and a new section titled “Clear a Room” described the same method using a “four-man fire team” that was detailed in the 2000 Ranger Handbook. When battle drills were written back into infantry doctrine in the 2016 version of FM 3-21.8, Battle Drills 6 had returned but with a slight name change—“Enter and Clear a Room”—and described the four-man stack method.

More than Just Doctrine and More than Just a Single Drill

The bigger problem represented by the video of the 10th Mountain Division soldiers is not the soldiers doing Battle Drill 6 wrong, but the multiple noncommissioned officers standing above them not identifying the major safety violations and tactics errors. Those mistakes should have been corrected in dry and blank training sessions long before live rounds were loaded into weapons.

Sparked by special operations forces’ training priorities and reinforced by experiences in 1993 during Operation Gothic Serpent—better known as Black Hawk Down—in Mogadishu, Somalia, the special operations community created multiple urban warfare courses. These courses, which still exist today—like the Special Forces Advanced Reconnaissance, Target Analysis, and Exploitation Techniques Course (SFARTAETC), Special Forces Advanced Urban Combat (SFAUC), and others—ensure CQB skills in special operations soldiers and noncommissioned officers are core competencies.

While conventional Army units slowly adopted CQB tactics into infantry doctrine and drills—and after 2000 required all soldiers train the new Battle Drill 6—they did not establish a robust system to ensure the tactics were learned, taught, and standardized across the greater Army. Neither the conventional infantry community nor the entire Army ever produced a school like the ones attended by special operations forces to ensure standardization of the drills. There are instances where individual units created programs—such as, interestingly a 10th Mountain Division Urban Combat Leader Course—but these efforts usually only lasted a short duration before being closed. Army units did send soldiers to the special operations courses, but it was never enough to ensure the Army had the resident knowledge to accurately train the tactics across the entire force. So without properly trained cadre from some type of urban master trainer school, unit training was often influenced by word of mouth from individual experiences more than a standardized tactic. So, it was not just the lack of ammo and training time Hooker identified that led to situations of Battle Drill 6 being done incorrectly. Actually, there are plenty of infantry and Army units that train, resource, and execute the drill to high levels of proficiency. It does take adequate time and resources, but it also takes trained noncommissioned officers. Battle Drill 6 (or any other urban tactics the Army wants to use) is easy to do but hard as hell to do well. It requires extensive training, a lot of shooting, and tons of live-fire drills. There are no shortcuts here.

Another main point Hooker missed is that Battle Drill 6 is not just for counterterrorism operations in permissive environments. The cases made against Battle Drill 6 are usually made by people who are addressing it in a single context, absent its high-intensity doctrinal history and usefulness. Yes, the Army missions in Iraq and Afghanistan did include years of executing intelligence-driven, precision raids in mainly permissive environments requiring complete surprise, speed, and entry from multiple unexpected directions described in CQB tactics. But Battle Drill 6, when applied as part of a full program of urban warfare training, can be adapted to match higher-intensity situations in a fully combined arms approach.

Nostalgia Can Be a Dangerous Thing

The tactical approach that Hooker seems to favor resembles a reversion to the tactics outlined in FM 90-10-1 along with the conceptual framework and assumptions about urban combat that underpinned them. FM 90-10 and FM 90-10-1 envisioned a depopulated and wrecked cityscape with few rules of engagement (ROE) restrictions on the application of firepower. It is a mental picture that evokes the Battle of Aachen (where the attacking Americans’ catchphrase for the operation was “Knock ’em all down” as they arguably not only did not avoid collateral damage, but sought to cause it), Seoul, Hue, or even Stalingrad. (The likeness with Stalingrad in particular is perhaps not surprising as many of the tactics presented in FM 90-10-1 seem closely related to those pioneered by Soviet General Vasily Chuikov’s 62nd Army as they ground down and ultimately destroyed German Field Marshal Friedrich Paulus’s forces in what many believe to have been the European Theater’s key inflection point during World War II.)

The problem is that the apocryphal city in FM 90-10-1 bears little resemblance to the teeming, pulsing, complex cities that the Army has actually fought in over the last thirty years. It did not take long in the modern era for this dissonance to give way to CQB. It was not just urban doctrine that was changing, but the world in which soldiers were deployed—a world with cities like Panama City, Panama; St. George, Grenada; and Mogadishu, Somalia where US forces found themselves operating.

When US forces assaulted Panama City in 1989 during Operation Just Cause, infantry units stepped into the world where FM 90-10-1 tactics conflicted with modern realities. Infantry in Panama City, like those in subsequent city fights, encountered people—hundreds of thousands of them—intermingled with enemy forces who almost invariably treated uniforms or identifying articles as quaint anachronisms. The “chainsaw” approach Hooker espoused—whereby infantry act as a chainsaw, not a scalpel—was inappropriate then and it is even more so now. While there is an interesting and quasi-theological argument that responsibility for civilian casualties lies with the side that undermines noncombatant immunity by wearing civilian clothing and embedding itself in the population, it is a proposition unlikely to gain significant traction in the current information environment. Troops in all our fights over the last thirty years have sought to minimize civilian casualties through the application of precise firepower and have still been pilloried when noncombatants have been killed. It does not take much guesswork to anticipate the reaction of global and domestic audiences when they receive nearly instant news through digital feeds of city inhabitants encountering a US Army infantry “chainsaw.” Drafted in an era before advancement in night vision, precision guided munitions, drones, and a full suite of modern combined arms weapons and tactics, FM 90-10-1 techniques proved profoundly unsuitable and inadequate for high-intensity warfare in densely populated urban areas like Panama, Mogadishu, Baghdad, and others.

While Hooker is completely correct that infantrymen should not be conducting hostage rescues or using counterterrorism environments as their mental starting points for future urban battles, reverting to the tactics of FM 90-10-1 only works if everyone encountered in a building is a combatant. This is not an assumption soldiers can make.

Relatedly, while the now-infamous 10th Mountain video shows significant safety and tactics shortfalls, the previous FM 90-10-1 methodology was arguably no safer. Room clearing with those techniques—their heavy use of grenades and bursts of fire in every room—put prodigious amounts of minimally directed metal in the air in confined spaces, with predictable results. As Hooker accurately notes, real bullets ricochet and go through walls, and in the lightly constructed, ramshackle buildings common across the developing world, so do grenade fragments. To be sure, when infantry have identified an enemy-held structure, the first tool to defeat that enemy should not be stacking outside the door. As soldiers have learned in recent battle, all available firepower and tools are used before entry. But eventually, the room still has to be cleared.

The Amorphous Nature of Battle Drill 6

Hooker seems to view Battle Drill 6 as not merely a room-clearing technique, but as a mental shorthand for an overarching philosophy of urban fighting that (he seems to believe) applies unnecessary limits on American firepower and places young infantry soldiers at elevated risk by preventing the full application of US fires and combat multipliers. This is a common mistake.

Much of this initial reticence stemmed from a misunderstanding of what Battle Drill 6 is—and what it is not. Put simply, Battle Drill 6 is a room-clearing battle drill, period. It does not encompass the entirety of CQB or urban warfare doctrine, nor does it in itself make any prescriptions regarding ROE, schemes of maneuver, or using (or abjuring) various combat enablers.

It instead offers the leader a scalable set of options applicable across multiple levels of combat intensity. The use of grenades is not forbidden—in fact Battle Drill 6 states, “If the unit is conducting high-intensity combat operations . . . a Soldier of the clearing team cooks off at least one grenade (fragmentation, concussion, or stun grenade)” and CQB tactics as originally envisioned make extensive use of explosive breaches from surprise locations. There is nothing in Battle Drill 6 that prevents a commander from, to borrow Hooker’s example, putting a main gun tank round through an entry point. There is nothing that bans the use of artillery, mortars, attack helicopters, or close-air support. If, however, these methods and tools are not appropriate under the tactical circumstances, infantry room-clearing tactics simply offer the leader a fuller repertoire of techniques to use in conjunction with all available assets.

There is also no inherent contradiction between CQB doctrine and the kind of bold, aggressive, and firepower-intensive tactics embodied in the 2003 “Thunder Run” or the 2004 Second Battle of Fallujah. Tactics are adapted to the context of the situation. While soldiers and Marines during the Second Battle of Fallujah did adapt their entry methods by using tanks, infantry fighting vehicles, mortars, and artillery to attack enemy fighters in buildings, they still had to search and clear the rooms of over thirty thousand buildings—in fact, one hundred squads had over two hundred firefights inside rooms.

Hooker seems to have inflated Battle Drill 6 into a more extensive doctrinal artifice on which he then hangs a set of concerns about excessive restrictions on US firepower that endanger our troops. This seems to conflate doctrine and tactics with specific leader decisions about ROE and the use of fires. CQB does not automatically restrict these enablers, though. Again, Battle Drill 6 is a room-clearing technique, nothing more. And it is definitely better overall, when trained properly and with varying conditions, than the one it replaced.

The Battle Drill 6 After Next?

Ultimately, Hooker is presenting a false choice. He would clearly hope to avoid having infantry fight in grinding, casualty-intensive urban combat and views conventional infantry as unsuited for room clearing in particular. His views are understandable, and he is treading a well-worn path here—writers stretching back to Sun Tzu have cautioned commanders against fighting in cities. What was often unavoidable in even overwhelmingly agrarian societies such as China during its Warring States period is even more likely so in today’s rapidly evolving urban settings. While perhaps things like artificial intelligence and other future technologies may in the not-too-distant future reshape our tactical options, for the time being infantrymen will have to fight in cities and will therefore need to clear rooms.

The real question is not whether to do Battle Drill 6 or CQB or not to. It is whether we decide that Battle Drill 6 and CQB are not germane to how infantrymen will fight in cities. If not, then what will replace them? What would be our conceptual framework going forward? Hooker rightly considers Fallujah an unattractive model for future urban fights, but for the wrong reasons. Over 90 percent of the city of Fallujah was emptied of its civilian population before the battle. That is unlikely to be the situation in future warfare. But which model is more palatable and more likely to achieve our desired political and military end states? Even with more destructive tactics of first placing high explosives into known enemy structures, rooms still have to be cleared.

What are the alternatives to room clearing? Complete destruction of cities using wide area artillery and aerial bombings such as Aleppo or Grozny when enemies embed into urban terrain?

Among the few techniques Hooker offered as alternatives were to simply use high explosives to clear rooms or conduct tactical callouts. It is not clear that applying even more firepower will be any safer for our troops. World War II armies learned to their detriment that reducing a building to rubble did not always simplify its clearance but rather provided additional rubble fortifications to clear. Ironically, the callout (surrounding a building or entire village with known enemy inside it and waiting for them to come out—essentially besieging it) was developed during counterinsurgency operations where the environments were mostly permissive and the mission variables (mission, enemy, terrain and weather, troops and support available, time available, and civil consideration) permitted sitting around and waiting for a single enemy to walk out. These conditions are also unlikely to be present during future urban warfare. Furthermore, a stationary unit conducting a callout is also subject to outside counterattack, indirect fires, snipers, and even vehicle-borne improvised explosive devices.

These significant disagreements with Hooker’s position and reasoning notwithstanding, there is value in his opinions starting a needed conversation. His article highlights tough questions we should be asking as more and more warfare has moved into urban areas. Soldiers should not be exclusively training room clearing under conditions of permissive environments or counterterrorist operations. Battle Drill 6 should not be the mental starting point or ending point for preparing Army formation for the wide range of tactics and skills needed in high-intensity urban combat. Urban warfare is a combined arms fight and requires frequent, realistic training to standard, and it requires soldiers to adapt to conditions that force a variety of tactics.

The bottom line is that soldiers will have to continue to clear rooms. That will not go away. In fact, the need will likely increase. Battle Drill 6 is useful when trained correctly and to a standard proficiency level as a tool to build on and adapt. Soldiers in the next battle will be required to close the distance to buildings—many fortified—clear them, and hold them using many tactics, techniques, and procedures based on the enemy, ROE, and urban environments they encounter.

Urban combat is tough, bloody, and difficult. It cannot be avoided. Urban battles consume time, supplies, and soldiers at an alarming rate. In the modern operational environment, however, we are likely to see many more battles in cities, not fewer. Despite Hooker’s skepticism, Army urban warfare tactics have actually evolved to match the character of warfare after the end of the World War II. We can’t throw the baby out with the bathwater in room clearing. We must continue to train for the full range of combat in densely populated urban areas.

John Spencer is chair of urban warfare studies at the Modern War Institute, co-director of MWI’s Urban Warfare Project, and host of the Urban Warfare Project Podcast. He previously served as a fellow with the chief of staff of the Army’s Strategic Studies Group. He served twenty-five years as an infantry soldier, which included two combat tours in Iraq.

Rich Hinman is a 1988 USMA graduate and a retired infantry officer with twenty-eight years of active and reserve service. He is currently a Foreign Service Officer with the Department of State serving in Kabul, Afghanistan.

The views expressed are those of the authors and do not reflect the official position of the United States Military Academy, Department of the Army, Department of Defense, or Department of State.

Image credit: Sgt. John Yountz, US Army