As the global population evolves toward a denser, more urban-centric environment, the battlefield landscape will likely follow suit.  Where the US armed forces of the twenty-first century once militarily dominated the rural landscapes of Afghanistan and the deserts of Iraq, the fight for military objectives will increasingly focus on population centers in the decades to come.  Of course, urban operations are not new to the US soldier or Marine.  Brave Americans have fought valiantly from the Battle of Hue City in Vietnam to Mosul in the ongoing fight against ISIL.  However, the cities of tomorrow will present new challenges where titanic populations and infrastructure density will combine with near-instantaneous flow of information to create a leviathan of complexity for the armed forces.

Current doctrine does not address the unique fabric of crowded urban areas of operation, though ongoing research, directed by the chief of staff of the Army, aims to address these shortfalls.   A 2014 Strategic Studies Group (SSG) report maintains that the US Army stands ill prepared to respond to and operate within complex cities, even as these areas become increasingly strategically significant.  Specifically, the SSG report argues, “the problems found in megacities (explosive growth rates, vast and growing income disparity and a security environment that is increasingly attractive to the politically dispossessed) are landpower problems.  Solutions, therefore, will require boots on the ground.”  Given this assessment, prioritizing the study of cities and their internal structures is vital to preparing the force to fight and win future wars.

The Rise of Cities

In his 2013 book Out of the Mountains, counterinsurgency expert David Kilcullen identifies four demographic “megatrends” that fuel the growing climate of conflict in urban areas.  Foremost, general population growth will adversely affect economic efficiency as resources become scarcer.  The current global population is approximately 7.3 billion and is projected to balloon to 8.5 billion by 2030.  Notably, the largest share of this growth will occur in forty-eight states presently designated as least developed countries by the United Nations—part of the “global south.”.  Among these forty-eight, twenty-seven of which are located in Africa, the population is expected to double by 2050.  The concentration, therefore, of rising population growth in the poorest countries will strain governments’ ability to satisfy basic service requirements such as housing, water, and gainful employment.  The search for resources and opportunity inevitably leads to urban environs.

This is Kilcullen’s second megatrend, urbanization. This migration of people into more densely packed cities further concentrates the demand, and subsequent competition, for resources.  Currently, the number of cities with a population of at least one million inhabitants stands at 512 worldwide.  Forecasts project that this number will rise to 662 by 2030.   Similarly, “megacities” with a total population of at least ten million are projected to increase from thirty-one to forty-one within the same timeframe.  Unsurprisingly, the locations of most of these cities coincide with the areas of fastest population growth: rapid urbanization predominately occurs in least developed countries in Africa and South Asia.  With urbanization projected to grow at 4 percent per year through 2030, increased vulnerability to disease, famine, unsanitary living conditions, and other perils threatens stability to an ever-increasing share of the global population.

Third, littoralization describes the trend of specific population growth in urban centers in close proximity to coastlines and riverine areas.  While access to water necessarily precedes settlement, it also places growing numbers of people inside of severe weather zones.  UN data estimates that 15 percent of cities are vulnerable to two or more types of natural disaster (floods, droughts, earthquakes, landslides, etc.).  Of those, twenty-seven total cities remain vulnerable to three or more types of natural disaster.  The category 5 Hurricane Matthew in October 2016, for example, destroyed in excess of 210,000 homes in Haiti alone, causing an estimated 1.9 billion dollars in damages.  The damage and spartan conditions the hurricane left behind enabled a cholera outbreak, which afflicted nearly 10,000 Haitians.  Though the effects of this event hardly resonated outside the Caribbean states, the scale of suffering illustrates the magnitude of the threat to concentrated, vulnerable populations clustered along coastal areas.  Were a similar disaster to strike Singapore or Tokyo, the net loss of economic and trade capacity would have worldwide consequences.

Finally, connectedness describes the expansion and deepening of links within and between cities, a dynamic tied to economic globalization and ubiquitous contact of populations via globally linked communications infrastructure.  Access to these “global systems of exchange” drives increasing reliance of people, resources, and organizations on the city domain.  Contact with this mass market proves valuable to businesses and political forces alike.  Any requirement for human interaction, therefore, encourages migration to the city.

US Boots on the Ground?

These trends merely illustrate the continuing rise of cities over the next decade.  Though cities offer endless positive opportunity to global society, they will also present increasingly important centers of gravity, attracting a range of conflicting forces and adversaries.  Under what circumstances, then, would US armed forces find themselves deployed in this arena?  America’s post-9/11 wars have already drawn US operations towards cities, where irregular forces and proxy adversary networks recruit and resource, simultaneously relying on the sanctuary of anonymity.  But future US military operations in cities may not be exclusively tied to counterinsurgency or the counterterrorism fight.  The rise of cities will focus national foreign policy objectives on these hubs of economic and social activity regardless of the adversary or nature of the military objective. Of course, a range of political considerations will always inform foreign policy, but several plausible scenarios exist that would bring the US armed forces onto dense urban terrain.

Perhaps the most likely scenario would see the military deploy to assist with humanitarian relief following a natural disaster event.  Consider the activation of the 82nd Airborne Division in the wake of the 2010 earthquake that devastated Haiti.  Within weeks after the 7.0-magnitude quake, which struck 25 kilometers south of Haiti’s capital city, paratroopers deployed to Port-au-Prince to assist with the international humanitarian relief effort.  The disaster left 1.3 million Haitians homeless and destroyed an estimated 60 percent of Haiti’s administrative and economic infrastructure.  Though Haiti warmly welcomed US-led relief, oversized mobs of displaced persons quickly tested the limited assets available to the paratroopers, who balanced providing life-sustaining aid while fending off bedlam.  Cities like Port-au-Prince underscore this truth: that in the density of the city environment, the negative effects of resource scarcity become more pronounced, especially in the wake of disaster.

At home, Title 10 activation of a Defense Support to Civil Authority (DSCA) mission allows US armed forces to be called on to “to save lives, prevent human suffering, or mitigate great property damage” in the United States.  In 2012, for example, active-duty troops joined National Guard soldiers in the relief effort in and around New York City that followed Hurricane Sandy’s landfall. US Marines from the 26th Marine Expeditionary Unit even landed on Staten Island from the USS Wasp. The hurricane shuttered businesses and cut off critical transportation and supply links due to flooding.  An estimated 375,000 people were forced to evacuate from Manhattan island, 1.5 million New York residents lost power, nineteen billion dollars in damages were caused in New York City alone, generating mass disruption to this vital hub of global economic activity. A US response to a disaster abroad could easily see US service members in a remarkably similar role in a foreign megacity, but with the added dynamic of operating in an unfamiliar environment and forced to contend with myriad security and stability challenges, both cause and exacerbated by the massive disruption, that were not present in the Hurricane Sandy response.

A US Army deployment to an area of dense urban terrain abroad might also be centered entirely on combat operations.  Taking a relevant example from current global affairs, the Republic of Korea hosts about fifty million people, 10.29 million of whom reside within the city limits of Seoul.  This city boasts the fourth largest economy of all world cities, and is located only thirty-five miles south of its hostile and presumed nuclear-armed northern neighbor.  Certainly, pending war with North Korea would significantly threaten this bustling driver of business and trade, and potentially appeal to US military involvement.  Aside from assistance to support non-combatant evacuation operations, or CBRNE cordon and clean up, an act of war could also encompass wide-area security tasks, or even defensive operations inside the city.

Whether humanitarian assistance, direct combat, or any point between, clearly US ground forces must prepare and train within the context of the dense urban fight.

Lessons from New York

The likelihood of cities as future areas of operation has already prompted review by the US military.  The Maneuver Center of Excellence at Ft. Benning has developed a week-long immersion learning experience that brings Career Course captains to New York City to develop their thinking about how tactics, techniques, and procedures (TTPs) overlay on dense urban terrain.  During an April 2017 trip, the group of captains applied a tactical eye to the varied terrain of New York City.  Several of the observations they made are instructive and should inform future development of TTPs optimized for dense urban environments.

First, cities’ high-rise structures challenge the maxim that the “high ground” presents advantageous terrain during military operations.  Limited floor space and exfiltration routes may trap a unit by restricting their maneuverability.  In addition, units may quickly exhaust the manpower required to “dominate” this terrain by fighting continuously along vertical axes.  Success in high-rise buildings might depend on units’ ability to co-opt local expertise.  For example, some towers incorporate pre-programmed repeater systems for use by first responders to overcome communications outages, accessible only by appropriate staff.  Such technology could be crucial for military units communicating between top floors and street level, but would require tapping the knowledge of building administrators and security staff.  Furthermore, some sophisticated structures incorporate physical safeguards— blast walls, blast-resistant windows and, perhaps, or low-lying stories of unoccupied floors to mitigate risk of targeted attacks—into their design, which could provide adequate protection for headquarters elements if required to hold terrain inside the city.

Second, on the street level, movement through city corridors is severely restricted and completely determined by the relative layout of buildings and roadways.  Therefore, the work of denying “freedom of maneuver” is half achieved by the city itself, before any opposing force is applied.  High-rise structures pose similar challenges to air operations, creating an urgent need for manned/unmanned teaming to cover all dead space with observation and direct fires.  Masses of tall buildings form urban canyons that create unique wind patterns for rotary-wing aircraft that differ than air conditions “above” the city.  Drones provide a far more effective tool due to their relative size and maneuverability within these building corridors.

Third, and similarly, the same concept extends to the main weapon systems on most combat vehicles, which will not be able to traverse all potential threats.  Such a large number of avenues of approach and potential defensive vantage points would overwhelm even the most skilled target acquisition systems and techniques in current use.  Isolation, understood as denying an enemy freedom of movement or contact with supporting forces on a given piece of terrain or building, is difficult on one plane, but almost impossible for a single tactical unit on a city’s multiple planes—a complex network of avenues, cross streets, and alleyways, sandwiched between subterranean tunnels below and multi-story towers above.

Finally, the expansive subterranean domain provided by immense networks of subway tunnels, working train lines, steam and wastewater pipes, and electrical grid substructures is wholly unique to cities.  This network effectively doubles the available routes for a force to move around in, since in many major cities, there are tunnels under every street.  Means of communication underground are almost invariably limited to hardline “mine phones,” or a deliberately established system of FM repeaters.  Visibility relies on access to electricity, supplied by either an existing grid, an industrial generator, or battery power.   Likewise, tunnels are vulnerable to groundwater flooding for cities in littoral areas, creating an additional complicated but vital planning factor.

A reliable air supply is an often-overlooked factor in subterranean operations.  For a tactical unit operating underground, resourcing oxygen is an imperative for mission planners.  Most large developed substructures are equipped with ventilator units located aboveground, which should be considered critical infrastructure.  However, these machines likewise require a large power source.  If electrical power is unavailable, the ability to conduct sustained subterranean operations must incorporate alternative means of air supply.

Another consideration is the depth of tunnels relative to the street.  In many cases, subsurface avenues of approach are the safest means of infiltration into a city, with substantial overhead cover and limited observation of a force’s movements.  While most tunnels will allow dismounted movement throughout, factors like tunnel width, surface layer composition, and exit locations will determine whether vehicles can also be moved beneath the surface—vehicles whose protection and firepower those dismounted forces might require. An understanding of each of the specific types of tunnels that underlay a city is thus critical.

The Way Ahead

As the terrain analysis of New York City makes clear, developing and refining new TTPs is critical. But, the tactical aspects are only a launching point.  Several strategic reflections also bear consideration.

Military planners should revisit force size construct requirements, which will change based on the density and scale of a city.  Common mission tasks such as “block” or “isolate” will drastically change when overlaid on dense urban terrain, where infrastructure significantly reduces maneuverability and observation, and masses of people far outnumber the standard infantry unit.  The US Census Bureau estimates that New York City (all five boroughs) has a population density of 10,500 people per square kilometer, mostly concentrated in Manhattan, with around 26,800 people per square kilometer.   These numbers are on par with cities like Mogadishu (26,800), Mumbai (26,300), and Al-Raqqa (25,400).  Population control in the event of an emergency-induced mass panic can rapidly render combat units ineffective.  The multi-domain spectrum described above likewise reduces the effectiveness of certain military vehicle assets.

Furthermore, recognizing that city life relies on a consistent “flow” of resources, key terrain within a city will largely coincide with supply lines and logistical networks.   Acknowledging the city’s “metabolism,” as David Kilcullen has put it, suggests that current strategies such as “clear/hold/build” in a counterinsurgency might not be effective—and could even be counterproductive—in urban terrain.  Operating within a city necessitates yielding some control to the organic function of the city—domination of terrain may not occur in the physical space, except by controlling the inflows and outflows of resources, people, and their means of transportation.

Genuine understanding of the capabilities (and limitations) of US military action in the city environment should focus operations on achievable outcomes and deliberately prevent mission creep. The joint, interagency, intergovernmental, and multinational nature of city-bound operations requires interagency crosstalk; active coordination and distribution of mission tasks across the myriad of battlefield players is vital.  Defense assets certainly offer mass manpower and (in appropriate cases) combat power.  However, the likelihood of combat operations in a world city remains relatively low compared to other missions such as emergency disaster response.  For that matter, critical local knowledge and experience provided by various municipal agents must be incorporated to achieve any operational success.  Knowledge of high-rise search-and-rescue techniques is most likely to reside in fire departments, for example, and a means of leveraging this and other expertise should be developed. Within the DSCA framework, this would take the form of direct partnering. But when operating abroad, it might mean cross-training with US law enforcement and emergency services before deploying or integrating foreign departments into operations on the ground.

Working with local agencies, whether in a DSCA scenario in the United States or abroad, also plays an important optics role. In the former, where civilian authority remains paramount, this is of course, also a legal issue.  Returning to the example of Hurricane Sandy, government authorities sought to respond swiftly and avoid the perception of inaction during 2004’s Hurricane Katrina.  However, when Marines disembarked from the USS Wasp onto Staten Island, many reports labeled it an “invasion,” calling into question the authority and authorization for deployment of federal troops on US soil.  It is not hard to imagine similar scrutiny—but with the potential for serious repercussions—applied to US military action on foreign soil, despite the best intentions.

Fundamentally, cities are human domains.  No matter how complex the physical terrain of cities’ infrastructure, the US military must recognize that future military objectives in urban areas will be deeply embedded in the context of relationships.  While the development and ongoing refinement of tactics optimized for dense urban terrain is critical, understanding the intricacies of interactions between the population, host-nation forces, local authorities, US personnel, and other actors is equally so.  Cities are rising, and conflict will inevitably find its way to them. The US armed forces cannot afford to be unprepared.


Capt. J. Alexander Thew is a US Army infantry officer and student at the Maneuver Center of Excellence, pending assignment to the 82nd Airborne Division. Capt. Jerome J. Lademan is a US Marine infantry officer and student at the Maneuver Center of Excellence, pending assignment to the 7th Marine Regiment. The views expressed in this article are those of the author and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the US Government.


Image credit: United Nations