“It became necessary to destroy the town to save it.”

That’s how a US Army major during the Vietnam war described the decision to use massive amounts of firepower, to include aerial bombs and artillery, while attacking approximately 2,500 Viet Cong who were besieging the city of Ben Tre and its surrounding villages. Vietnamese provincial authorities assessed that 85 percent of the city was destroyed and up to 1,000 civilians were killed in the operation.

That contention didn’t only apply to Ben Tre, though. The military continues to struggle with built-up environments with civilians present—a struggle that grows dramatically alongside the scale of the town or city in question. The fact that “it becomes necessary to destroy a city to save it” highlights the destructive tactics that have almost always been required to liberate a city from enemy forces that choose to defend in urban areas. The recent battles in Aleppo, Mosul, and Raqqa show how this reality persists.

In fact, the story of Ben Tre pales in comparison to recent urban battles. The 2017 battle to liberate Mosul, Iraq came after Islamic State fighters seized and had occupied the city for over two years. It took nine months, one hundred thousand Iraqi security forces and a large contingent of US military support to take Mosul back. An estimated 826,000 Iraqis were displaced by the battle. When the former residents of Mosul returned, there was little left. Over forty thousand homes and sixteen neighborhoods were completely destroyed. Authorities estimate the cost to rebuild all the destroyed cities in Iraq to be over $88.2 billion, $42 billion just for the province that includes Mosul, the country’s second largest city. The fight to reclaim Mosul was not led by, or fought with, US forces, but Iraqi forces were supported by US intelligence, airpower, and artillery fire. Nevertheless, there is little reason to believe a US military operation would have used different methods or would have resulted in substantially fewer civilian casualties and less destruction.

When I attend conferences on urban combat I am frequently asked questions about protecting civilians in urban warfare and why urban combat is so uniquely destructive. I have also been asked why the military’s specific weapons are employed in certain tactical scenarios (e.g., “Did it really take a hellfire missile to eliminate one sniper?”). But, in all these events, I have never been asked the more straightforward question: Why must the military destroy a city to save it?

These discussions are often raised in the context of the efforts of the United Nations and humanitarian aid organizations to prohibit the use of explosive weapons in urban combat. Statistics are cited showing that during recent battles in the Middle East, three out of every four victims of explosive weapons were civilians. As an article published by the UN’s Office for the Coordination of Humanitarian Affairs put it, “the use of air-dropped bombs, artillery, mortars, rockets, IEDs, and other explosive weapons in towns and cities kills and maims civilians, and destroys and damages their homes, hospitals, schools, electricity grids and water and sanitation systems — the critical infrastructure they rely on.” Even the UN secretary-general has publicly called for all parties of a conflict to avoid using these weapons in populated areas.

Context in war is everything. Urban warfare can include any of the many missions that fall within the full range of military operations. It might be a humanitarian aid operation that involves small battles against insurgent or criminal forces fighting over aid resources. It could be operations against terrorist, guerilla, or insurgent forces conducted during a larger stability operation against a single or (more complexly) multiple anti-government and often competing factions. Or it could take the form of an all-out assault on a city occupied by enemy forces. On top of this, the political situation, rules of engagement, number of enemy forces, enemy capabilities and tactics, presence and status of civilians, and the capability and size of the military organization conducting the operations all further contribute to define the specific character of warfare.

The enemy could be a conventional military force, like the North Korean Army during the 1950 Battle of Seoul or North Vietnamese regulars in the 1968 Battle of Hue. It could be a nonstate paramilitary organization with military training and capabilities, like the Chechen rebels in the battles for Grozny in 1994–1995 and 1999–2000. Or it could be a well-equipped and prepared terrorist organization, like the Islamic State in the battles across Iraq and Syria since 2014. Regardless, the most destructive urban battles usually occur when an enemy force decides to defend from within a city and an opposing force has decided the city must be reclaimed or the enemy eliminated.

Cities represent the toughest and most complex environment within which armed forces conduct military operations. The city’s defenders have the advantage, providing them large areas of restrictive terrain to incorporate into their defensive plans. Defending forces can also use the terrain to funnel military forces into dense areas that break up formations and limit their ability to conduct maneuver warfare—the preferred way of operating for Western military forces. Defenders can literally turn every building into a battlefield with a single sniper or small group of fighters that attacking forces must either fight or destroy.

The history of urban warfare is full of cases of tenacious enemy forces using a single building or a series of buildings to hold off far superior attackers. In the 2004 Battle of Fallujah, it was the “House of Hell,” where just a few suspected Chechen fighters turned a house into a death trap for the many Marines trying to take it. During the 1942 Battle of Stalingrad, small groups of Russian soldiers held single buildings—like a grain elevator and an apartment building (named Pavlov’s house)—for months against German tank, artillery, and infantry assaults.

To understand how a military will execute an operation to reclaim a city, a student of war must understand both military doctrine and historical case studies. Every city is distinctive, every enemy is unique, and therefore every battle is different. But by looking at current doctrine alongside a survey of history, we can identify some commonalities in approaches and even make assertions on the likely way the military might best fight in cities in the future.

Destroying Cities to Save Them: Inside Military Doctrine

US Army urban doctrine includes no specific guidance on how to recapture an occupied city. It does provide general characteristics, as well as things like sequencing of forces, task organization considerations, and recommended steps for urban offensive operations—which are precisely the same as offensive instructions for other environments.

In planning a major, offensive urban operation to liberate a city, the military will identify the form of maneuver and type of offensive task. The most common and likely form of maneuver and offensive task for this mission will be a penetration to conduct a deliberate attack. A penetration maneuver seeks to penetrate a prepared and comprehensive enemy defense at an advantageous and hopefully unexpected location. A deliberate attack is just that, one that is planned. It is the opposite of a hasty attack, in which a unit executes an unplanned attack to take advantage of a particular situation (e.g., discovering a previously unknown enemy location).

Doctrine recommends the following phases for deliberate attacks: reconnoiter the objective, move to the objective, isolate the objective, secure a foothold, suppress the objective, execute a breach (if necessary), clear the objective, consolidate and reorganize, and prepare for future missions.

To remove some of the jargon and simplify, if military forces seek to reclaim an occupied city they will:

attempt to remove or relocate all noncombatant civilian inhabitants prior to the start of the attack;

surround the city by blocking exits with tanks, troops, or aerial observation and fires to isolate and prevent enemy escape or resupply;

suppress key enemy targets such as command centers, logistical bases, or known key individuals with aerial bombs, artillery, or attack aviation;

breach any defenses the enemy may have established;

send a large formation of (preferably) tanks and mechanized vehicles with infantry soldiers to penetrate into the urban area from multiple directions;

and finally, begin clearing buildings with the infantry soldiers along a path to seize key objectives deep within the city.

Once military forces penetrate into an urban area, their formations are disaggregated by the dense physical terrain. This is where a majority of urban attacks rapidly break down into firefights between small groups of soldiers and enemy forces. Furthermore, small groups of attacking soldiers are often required to clear every room, from one building to the next, block by block.

When soldiers clearing buildings identify enemy forces, they will either deploy close-quarters combat techniques to enter and clear the enemy-held buildings or they will engage the structures with direct, indirect, and aerial-delivered munitions to kill the enemy forces inside. These munitions range from hand-carried weapons to vehicle-mounted direct-fire weapons, artillery, mortars, rotary- and fixed-wing aircraft, and even unmanned aerial vehicles.

Soldiers often begin urban assaults by attempting to enter and clear all buildings, because it allows them the ability to positively identify exactly what is in them. Frequently, however, after suffering casualties or when momentum slows and the soldiers are unable to dislodge or even reach the enemy inside the buildings, they resort to attacking buildings by fire.

It is important to point out the difference between planned and unplanned fire support. Planned fires involves a targeting process that identifies what locations are to be fired upon and when, includes collateral damage risk calculations, and even incorporates legal reviews of targets to be hit before and during the urban operation. Unplanned fire support is used by maneuvering forces to suppress or destroy known and suspected enemy locations, prevent enemy escape, and provide friendly forces freedom of maneuver.

Soldiers have more precision fire options than ever before—guided munitions, including the 155-millimeter Excalibur howitzer round, guided multiple launch rocket system rounds, and aircraft missiles and bombs with low-explosive yields. Soldiers will use the best tools they have available to accomplish the task at hand. For instance, the steep trajectory and minimum range of mortars, for example, make them attractive tools for urban combat because cities’ vertical terrain (i.e., tall buildings) can limit artillery fire and other types of munitions with flatter trajectories.

A vivid example of the difficulty inherent in entering buildings in major urban fights is described in detail in Reimagining the Character of Urban Operations for the U.S. Army, a summary of the 2004 Second Battle of Fallujah produced by the RAND Corporation. For example, after one Marine platoon had lost almost half its men clearing enemy-held buildings they decided they would not enter “houses anymore without [first] prepping with grenades or rockets, minimum a grenade.” In his post-battle interview, the commander of the 1st Marine Division, Maj. Gen. Richard Natonski, acknowledged an even greater shift. “Because of the intensity of the resistance and if we knew there were insurgents in buildings, in some cases we’d drop the structure before we’d risk soldier or Marine lives by sending them into buildings,” he said. “We used everything from tanks at close range shooting up the buildings to D9 armored bulldozers to 500-pound JDAMs [Joint Direct Attack Munitions].”

Destroying Cities to Save Them: The Historical Case

A survey of historical cases of urban warfare yields an array of important insights, the most significant of which has to do with the tools available to the forces involved in these cases. Maj. Gen. Natonski’s statement gives a sense of the types of tools his Marines were forced to use in Fallujah. But those Marines’ experience is far from unique.

There are very few tools—a compelling argument could be made that there are zero—in modern US Army formations designed for major combat operations in dense urban terrain. Major states’ militaries are designed and organized to fight other militaries on relatively wide-open battlefields, not in cities. And they are designed to destroy the enemy, not to liberate civilians or to ensure low collateral damage.

Major wargames that determine the capabilities and size of military formations primarily involve two state actors fighting a major battle in places like the open plains of Eastern Europe, deserts of the Middle East, or littoral areas of Asia and the Pacific. Military units are designed with capabilities optimized to destroy enemy forces in these environments. This means that there are no urban-specific units in the US Army—not a single one that is specifically dedicated to preparing for combat in cities.

Force design also includes factors of adaptability. While designed for major combat operations against near-peer threats (currently Russia and China) in a limited amount of settings, all US Army formations are expected to adapt to the full range of military operations, against all types of enemies (e.g., hybrid forces employing asymmetric warfare), and in all environments. This is why most Army units are called “general purpose forces” (as opposed to “special forces,” which are designed for a few special types of missions—unconventional warfare, special reconnaissance, etc.). While special forces do have the advantage of being regionally aligned—so at least they can focus their training to a more specific region—there are none focused on major urban areas.

Consequently, when faced with major urban combat to reclaim an occupied city, general purpose military units and soldiers attempt to adapt tools and tactics designed for other environments. Many of these tools—like tanks and Bradley infantry fighting vehicles that provide mobile protected fire or precision-guided munitions that limit collateral damage—do provide soldiers needed capabilities in urban environments. Others have to be greatly adapted from their traditional purposes, like howitzers being used to punch holes into walls.

Over time, the capabilities and force designs of the US military have changed (although the focus on state-based enemy forces and large, open environments has shown a remarkable staying power). Current combat planning scenarios may actually provide soldiers with access to less adaptable weapons and techniques than past force designs—a fact made apparent by an examination of historical cases.

Military units today have fewer tools to adapt to a major urban fight than they did, for example, during the Vietnam War. In the 1968 Battle of Hue, soldiers and Marines were asked to quickly adapt from jungle to urban fighting. Marine Corps Lt. Col. Ernie Cheatham did a quick review of urban doctrine and then directed his staff to collect as many penetrating and explosive tools as possible, to aid in the intense urban fight they were about to undertake. The tools available to him included the M50 Ontos (a 106-millimeter, six-barrel, self-propelled tank destroyer), the M67 “Zippo” (a tank equipped with a flamethrower), portable flamethrowers, tear gas, bazookas, 106-millimeter recoilless rifles, grenades, and plastic explosives.

Both flamethrowers and tear gas have been shown to be effective tools for clearing enemy forces from buildings without totally destroying them. Flamethrowers can penetrate small openings and fill fortified positions with both fire and smoke. Tear gas can force enemy forces to evacuate fortified positions within buildings, especially when the military objective is focused as much on reclaiming terrain as killing individual fighters. Today, soldiers have neither flamethrowers nor tear gas.

In 1978, the US Defense Department issued a directive that ceased the tactical use of flamethrowers. International efforts to ban the weapons gained support following the Vietnam War. Specifically, Article 35(2) of the 1977 Additional Protocol I to the Geneva Conventions states: “It is prohibited to employ weapons, projectiles and material and methods of warfare of a nature to cause superfluous injury or unnecessary suffering.” The most current treaty norms regulating incendiary weapons are located in Protocol III to the 1980 Convention on Certain Conventional Weapons.

While some experts believe flamethrowers could be legal in combat situations where no alternative weapons that would cause less suffering are available, the US military does not use them. Yet a look at the most recent cases of urban warfare makes clear why such tools are better suited to city fighting than most others available. In July 2017, while discussing the final firefights of the battle to liberate Mosul, Gen. Stephen Townsend, the current commanding general of the US Army Training and Doctrine, stated:

I saw things I have only ever read about in history books. . . . It was the last week . . . around July 10th. . . . Mosul had been cleared except for a 400 x 400 meter postage stamp. . . . Then it shrunk to 200 x 200. . . . It took about a week to take that. . . . The buildings had been turned into bunkers . . . rubble 20 to 30 feet on top of the first and basement floors. . . . You couldn’t build a better bomb proof shelter. . . . ISIS was dug in there and he wasn’t giving up. . . . On the last day I watched reconnaissance video feed of the final Iraqi assault. . . . There was an Iraqi bulldozer driver driving through that field of rubble and on each side of the bulldozer was a squad of Iraqi infantry walking along protecting the bulldozer and as ISIS fighters popped up out of the rubble, the bulldozer would turn towards them and bury them whole, infantry walking along would drop grenades in holes and shoot guys trying to fire rockets to knock it out. . . . We found ourselves wondering if we still have flamethrowers in our inventory, turns out we don’t, some armies do, but we didn’t, I couldn’t get my hands on flamethrowers fast or I would have.

Gen. Townsend highlights both the difficult, destructive nature of retaking a city from a determined enemy, as well as the need for tools like flamethrowers.

Tear gas has been banned as a method of warfare since 1997, when the US Senate ratified the Chemical Weapons Convention of 1993. To be sure, any use of chemical agents is a slippery and dangerous slope. But there is an important discussion to be had about where legal and normative boundaries are drawn. One of the first uses of gas in war was to clear trenches during World War I. One could draw similarities between the challenge of crossing open ground and that of entering and clearing trenches, bunkers, or buildings in urban environments. While tear gas is widely used for crowd-control purposes in urban policing, it is off limits to the US military in combat.

Bans on flamethrowers and tear gas were clearly made with the good intention of protecting civilians and preventing unnecessary human suffering. But the ban may have actually made the situation worse. Without these tools to clear buildings of fortified combatants, soldiers turn to the tools they have.

Artillery fire is one of these tools. Artillery rounds have the explosive power needed to penetrate buildings. Most recently, US Marines supporting the 2017 battle to liberate Raqqa, Syria fired more artillery in five months (over 35,000 rounds), than in any other Marine or Army artillery battalion since the Vietnam War. The Marines fired so many rounds that they burned out howitzer barrels, which, as any artillery soldier will tell you, is extremely hard to do.

Current Army doctrine rarely refers to historical urban operations as a way to prepare for future city fighting. These operations are also not as common in modern history as some people might think. Although the US Army has a long history of conducting some forms of urban operations, there have been few major combat operations specifically to recapture an occupied city (meaning an enemy force got there in advance and prepared a defense with the intention of holding ground) in modern history. The few examples include the 1968 Battle of Hue, Panama City in 1993, Baghdad in 2003, Fallujah (twice) in 2004, Ramadi in 2006, and Sadr City in 2008. Many examinations of urban warfare cite World War II battles—Stalingrad, Aachen, Manila, or Seoul—instead of more current history. But those older examples can be problematic for several reasons. The Battle of Stalingrad, for instance, was actually a meeting engagement that just happened to be pulled into the urban area and where the majority of the combat happened on the outskirts of the city.

Without sufficient focus on historical vignettes in urban doctrine, we’re left to assume doctrine writers have analyzed history and incorporated it into the doctrinal text. But this leaves us without knowledge on what adaptations were made by past units. How did they change their formations? How did they use the tools they had available? What went wrong and what went right? Without this understanding the soldiers that will fight the next battle are left to their own experiences and imagination.

There are, of course, sources of learning besides formal military doctrine—handbooks, lessons-learned pamphlets, and post-combat interviews. But doctrine is the military’s guide for preparing for the next battle and should be our primary resource to answering the question of why such destructive means are employed in urban combat. “Destroying the city to save it” is generally the only option doctrine affords and there is little offered to guide US forces in considering a different approach or what adaptations have worked in the past.

One should expect enemy forces, especially nonstate actors with limited concern for cities or their inhabitants, will continue to seek out the substantial advantages afforded them by urban terrain. Because military forces have not improved their ability to dislodge enemy forces from their urban defenses, they know that they will at least have success in the short term. Of course, a disciplined military trained in combined-arms maneuver, using tanks and infantry, will eventually prevail—but at major costs.

This sends a signal to the enemy and the world. Allies and partners who ask for US military support to recapture a city? Just know it will come at a major cost in terms of destruction and civilian casualties.

To be clear, I am not arguing for increasing the restrictions on military force in cities. Restricting the use of explosive munitions in urban areas would be catastrophic, prolonging urban conflicts that take an enormous toll on cities and their people. Rather, I am arguing that because cities are almost certainly going to be where fighting will occur in the future, US and other militaries must prepare and adapt. There needs to be an organized and deliberate study of specific types of urban operations (e.g., liberating an occupied city) that can be incorporated into urban doctrine. We must also explore other approaches to conducting major urban operations to quickly isolate and destroy enemy forces entrenched within urban terrain while also operating in a way to cause the least harm and lowest collateral damage to the city’s terrain, populace, and infrastructure.

The changes needed to decrease the destructive nature of military operations to reclaim an occupied city will not be small. New approaches will require investments in new approaches, technologies, equipment, organizations, and training designed specifically for major urban assaults, as well as policy changes to allow the use of different weapons like flamethrowers or tear gas. Without these changes, we can expect to have to destroy cities to save them.

John Spencer serves as the Chair of Urban Warfare Studies as the Modern War Institute and Co-Director of the Urban Warfare Project . He is a retired Army major who served twenty-five years as an infantryman, including two combat deployments to Iraq. Follow him at @SpencerGuard The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Army, the Department of Defense, or the US government.

Image credit: EU Civil Protection and Humanitarian Aid Operations