If we are entering an era where military forces will increasingly be called upon to operate in cities (and we are), it follows logically that the Army should begin preparing for urban terrain. But a quick scan of the global contemporary operating environment reveals the extraordinary diversity of urban landscapes. So what types of cities should we focus on?

Over the last few years, there has been growing attention within the US military on megacities—cities with ten million or more inhabitants. In 2014, the Army conducted a yearlong research project on megacities, which concluded that it is “ill-prepared” to operate—essentially, to conduct any mission—in a megacity. Other scholars have argued that mid-sized or even smaller cities are more important, especially if they’re perceived as likely spots of future military action. But while both individuals and centers within the Army continue to write, conduct research, produce studies, and hold conferences on the problems associated with operating in major cities, too little effort has been directed toward examining which specific cities around the globe the US military should pay closest attention to.

Many senior military and national security leaders have acknowledged both the military’s need to prepare for major military operations in cities, big and small, and its current inadequate capabilities. The current commander of the Army’s Training and Doctrine Command, Gen. Stephen Townsend, believes that “we’re going to see battle in megacities and there’s little way to avoid it.” In a similar vein, Chief of Staff of the Army Gen. Mark Milley has said, “It’s obvious you can’t predict the future with certainty, but there are certain things that I feel confident that we can articulate and we know will probably be true. . . . [The world is] rapidly urbanizing. . . . We need to man, organize, train, and equip the force for operations in urban areas, highly dense urban areas, and that’s a different construct. We’re not organized like that right now.”

But the sheer diversity among the world’s cities makes such preparation challenging. Yes, they have similarities, but each has remarkably individual qualities. Cities differ in population density—from the extreme of Mumbai’s 75,000 residents per square mile to less dense megacities like Los Angeles, where twelve million people are spread out over vast stretches, giving it a density of around 7,500 residents per square mile. But as a 2014 study on megacities points out, large urban areas can also vary drastically in a wide range of ways—from their historical and cultural contexts to their regional and international connectedness, resource flows, threat profiles, health, structural, and infrastructural complexity, and general ways of functioning. Gen. Milley is right: the US Army is not designed, manned, or trained for major combat operations in dense urban areas. But even if it wanted to optimize itself to operate in such areas, do we have an appreciation of the sheer diversity that distinguishes each city from others?

The World is Becoming more Urban, but the US Military is Not . . . Yet

According to the United Nations, in 2018 there were 548 cities with at least one million inhabitants, forty-eight with populations between five and ten million, and thirty-three that were home to over ten million. By 2030, these numbers are expected to jump to forty-three megacities, sixty-six with five to ten million, and 706 with over a million residents.

At a strategic level, though, this rapid urbanization is not reflected in military planning. The US military is in the midst of a major shift—a reorientation toward state-based, peer or near-peer adversaries after years of combat against nonstate actors in Afghanistan, Iraq, and elsewhere. But the strategic planning that is driving that shift is essentially separate from ongoing discussions about military operations in urban terrain—despite the fact that cities have long been the political and economic centers of gravity of the types of adversaries we’re now planning for.

Moreover, the resources and systems available leave little ability for units to compensate for this strategic oversight at the operational or tactical levels. Army doctrine makes clear that intelligence is particularly important in urban operations, and doctrine also does a reasonably good job of acknowledging that urban environments pose unique challenges to the intelligence warfighting function. It also points toward adjustments that urban operations might require—like emphasizing human intelligence given the density of both threat forces and noncombatants—and highlights how cities amplify the importance of civil considerations compared to rural areas.

But there are no urban-specific methodologies that equip intelligence personnel to truly provide commanders with the degree of understanding of a particular city that is necessary. The Army’s standard framework for analyzing mission variables—METT-TC (mission, enemy, terrain, troops available, time, and civil considerations)—is still used, as is the traditional PMESII-PT method (political, military, economic, social, information, infrastructure, physical environment, and time). Specifically with respect to civil considerations, the doctrinal means of conceptualizing these is captured in the acronym ASCOPE—areas, structures, capabilities, organizations, people, and events. Certainly this is more useful in populated than unpopulated environments. But at best this method will yield a cursory understanding of a city’s characteristics. It will not enable an S-2 or G-2 to do things like map the resource flows that keep a city functioning, identify the key individuals with knowledge of critical infrastructures, track the unique and dynamic mix of formal and informal power structures that keep it stable, or distinguish city-wide dependencies and vulnerabilities from hyper-local ones that come into play in a single neighborhood or on a single street.

Rectifying these deficiencies is important. But even when that is complete, an appropriate focus on urban environments must be placed within a context that acknowledges the diversity of cities. Each city requires a unique approach, from the strategic planning level down to tactical execution. Predicting the actors and locations of future wars is a complex activity, fraught with opportunities to get it wrong. But with a belief that there’s greater virtue in trying to do so than not, we ask the following question: What cities should the Army be conceptually thinking about as operating environments?

To be clear, this is not to say that any one of these cities is likely to host US military operations in the near future. But they each exhibit characteristics that argue for their inclusion on a list that is aimed at helping the Army move beyond thinking about cities as a monolithic operating environment and begin thinking about any single city’s unique vulnerabilities and the challenges each might post. Moreover, the list we have identified is not exhaustive, and the US military will be better off if others weigh in on the discussion. But compiling the list is one small step toward being prepared.

Criteria

The city is important to US national interests. These interests can be associated with US or global economic vitality, stability in a region important to the United States, or either existing or forecasted national security threats.

The city is a location US personnel would likely be present in or deployed to, either by force or request. This eliminates cities from consideration to which US assistance would not be welcomed or where US military involvement is highly improbable outside of major regional or global war.

The city is among those that the US military is least prepared for or has little institutional knowledge about, most likely because of limited historical US presence. This rules out US cities, which in any case would see US military involvement (in the case of an emergency, for instance) in a supporting role to state and local authorities.

The city has important links to the global economy. These include what Saskia Sassen has identified as global cities—hubs in a global, interconnected network by which information and money is transmitted. From 2014 to 2016, the three hundred largest metro areas in the world accounted for 67 percent of global GDP growth. The more that global economic infrastructure concentrates in major urban areas, the more important those cities are to US (and global) interests.

The city may become military key terrain—for example, major Eastern European cities that would be important to hold off a large-scale Russian advance or territory grab. While key terrain is very specific to military operations, it is reasonable to identify key cities in major combat plans that would be critical in conflict against near-peer competitors.

The city has uncontrolled or rising political instability. One major destabilizing factor is sudden population growth, something especially common in underdeveloped parts of the world. Whereas rapid urbanization has historically been largely correlated with economic growth, today the world’s fastest growing cities are in regions where economies are stagnant or in decline. These cities might also have characteristics of what Robert Norton has described as “feral cities”—those “with a population of more than a million people in a state the government of which has lost the ability to maintain the rule of law within the city’s boundaries yet remains a functioning actor in the greater international system.” Existing metrics, such as the urban “fragility index” developed by the Igarapé Institute in Brazil, assist in assessing cities based on this criteria.

The city and surrounding areas have a significant presence of armed groups (e.g., insurgents, gangs or other illicit criminal networks, or alternative power groups). Robert Muggah’s work on fragile cities helps capture the potential for urban failure because of crime, insecurity, and violence that are often catalysts for instability.

The city is extremely at risk to natural disasters. There are twenty-six major cities—including megacities Manila, Osaka, and Tokyo— that are at high risk of exposure to three or more major natural disasters.

The city is experiencing or at risk of an internationally recognized humanitarian crisis that could lead to US or international intervention.

The Cities

Given that criteria, which cities are among those the US military should be watching and studying? Again, the list below is not intended to be exhaustive. (Note: Cities on the list are not ranked.)

1. Caracas, Venezuela

Venezuela’s capital has been named one of the most dangerous cities in the entire world and has one of the highest murder rates. Most of the city’s violent crimes go unsolved, and the US government regularly issues warnings against travel to the city of 1.9 million (with a metro population of 2.9 million). Meanwhile, the city continues to experience rapid population growth amid nationwide economic challenges. All of this is now in the context of some of the greatest political instability Venezuela has experienced in years.

2. Mexico City, Mexico

With a population of 8.9 million (and a metro population of 21.2 million), Mexico City is the most populous metropolitan area in the Western Hemisphere and home to 20 percent of Mexico’s entire population. It is also among the world’s most vulnerable cities to natural disaster.

In September 2017, a magnitude 8.2 earthquake in southern Mexico left dozens dead and hundreds injured. The quake also broke apart a thirty-seven-mile-thick tectonic plate, a demonstration of the ferocity of the forces that lie underneath parts of the country. A large quake in Mexico City would be devastating. In 1939, an earthquake of similar magnitude killed nearly thirty thousand people in the vastly smaller Chilean city of Chillán. Such an event would stress and potentially overwhelm disaster response capabilities and potentially trigger a request for international assistance.

Mexico City’s growth—from 2.8 million residents in 1950 to more than twenty-one million today—makes vital efforts like providing water for the city’s population a remarkable undertaking, requiring a daily intake equivalent to a lake one meter deep, one kilometer wide, and nearly six kilometers long. The resilience of the mechanisms that underpin such efforts would be put under immense pressure by a disaster.

3. Sanaa, Yemen

Sanaa (population: 1.9 million) is the largest city in Yemen and the center of Sanaa Governorate. Although it is Yemen’s constitutionally recognized capital, the conflict in the country led to the city of Aden becoming the temporary capital in 2015. Sanaa is one of the highest capital cities in the world at an elevation of 2,300 meters and its Old City is a UNESCO World Heritage Site, making it dense with culturally significant structures—both of which would have operational implications for military forces.

Yemen has been embroiled in a bitter civil war since 2015 as the Saudi- and Emirati-led coalition supports the government of President Abd Rabbu Mansour Hadi against the Houthi movement that controls the capital, Sanaa. Twenty-four million people remain in need of humanitarian assistance and the United Nations warned in late 2018 that the country risked facing a “massive famine.” According to the most recent assessments, 63,500 Yemenis are experiencing catastrophic levels of food insecurity. Yemen is also home to the worst cholera outbreak in modern history, with over one million affected.

4. Karachi, Pakistan

With an estimated population of more than sixteen million and a metropolitan population reaching twenty-three million, Karachi is the world’s seventh largest urban agglomeration and the largest city in the Muslim world. At over sixty-three thousand people per square mile, it is among the densest megacities in the world.

Between 1998 and 2011, Karachi’s population more than doubled, the fastest growth of any metropolitan area in the world. In part because of this growth—around 45,000 migrants arrive in Karachi every month from around Pakistan—up to 65 percent of residents are estimated to live in slums. Vulnerable to climate change and prone to chronic problems with water access, unpredictable politics, and civil unrest, the city’s sheer scale raises the risk that small crises could spiral into one that Karachi’s (and Pakistan’s) authorities struggle to contain. Its role on the global jihadist landscape—the 2008 Mumbai attacks were monitored and coordinated from a control room in Karachi—raise the level of US interests in the city.

Finally, one worst-case scenario that continues to plague analysts that study the region is that of a “loose nuke.” Given that Karachi is home to a major nuclear plant (and two more reactors are being built nearby), the question of how the US might respond to such a scenario—and the impact the city itself would have on that response—if an important one.

5. Lagos, Nigeria

According to the Rockefeller Foundation’s 100 Resilient Cities project, Lagos (with a population of twenty-one million, compared to just 1.4 million in 1970) is especially susceptible to damage from rising sea levels and coastal erosion, which have already led to a decline in water quality, the destruction of drainage infrastructure, and an increase in incidences of water- and vector-borne disease. Coastal erosion has also hurt indigenous communities that depend on coastal resources for survival. Major possible shocks the city could suffer include disease outbreak, energy insecurity, infrastructure failure, unsustainably rapid population growth, and flooding.

Lagos is home to 60 percent of commercial and industrial ventures in Nigeria and generates 25 percent of the country’s total gross domestic product. Foreign investment (of which the United States is the largest source), especially in the oil and mining sectors, has produced considerable wealth that is clustered in Lagos. Yet 60 percent of the city’s population lives in poverty. As Nigeria’s commercial hub and largest city, Lagos also experiences many of the challenges that face Nigeria as a whole particularly acutely—ranging from terrorism and crime (including kidnapping) to corruption and general mistrust of the government.

6. Manila, Philippines

Manila, the Philippines’ capital, has a population of 1.7 million, but joins with fifteen other cities to form Metro Manila—which has a population of twelve million people (the extended urban agglomeration is estimated to be home to more than twenty-one million). During World War II, the city’s population was estimated at 684,000, but even as a much smaller city it became the site of one of the largest urban battles US forces took part in. One hundred thousand civilians died as a result of the fighting, and much of the city was completely destroyed.

Today, Manila serves as a vital hub in the world economy. It is also located on top of a fault line and especially vulnerable to typhoons. Because of these and other factors, it has been identified as the second riskiest city in the world in terms of its exposure to natural disaster risk.

7. Taipei, Taiwan

Taipei City—Taiwan’s capital and home to a population of 2.7 million—forms part of a large metropolitan area with a population of 7.4 million. With a modern and free economy and considerably less domestic political instability than many other cities on this list, Taiwan (and Taipei) are substantially less vulnerable to many of the challenges that might lead to US military involvement, in some form, in other cities around the world.

However, authorities in Taipei, Beijing, and Washington have performed a delicate balancing act for forty years. As China continue to rise as a global power, its historic claims to Taiwan could conceivably come into conflict with US security guarantees over the island—leaving the potential for a looming security crisis.

Of course, in the event that conflict over Taiwan breaks out, naval engagements are considerably more likely than US boots on the ground in Taipei. However, as a small island nation with a highly urban-based population, the unique logistical requirements required simply to keep Taipei functioning represent a powerful set of challenges.

8. Warsaw, Poland; Riga, Latvia; and Vilnius, Lithuania

Any of these cities—Warsaw (population: 1.75 million), Riga (population: 641,423), or Vilnius (population: 542,664)—on Europe’s eastern periphery could be central to an outbreak of war with Russia. One or more of the cities might be the base from which a westward advance of a Russian ground formation is blunted. Holding them, while NATO (including US) forces defended to buy time for reinforcements to arrive, could prove critical to forestalling another annexation of territory akin to that of Crimea in Ukraine.

Beyond varying in terms of both population and geographic size, however, each of these cities would require a unique approach to holding or recapturing. Riga, for instance, is a coastal port city, while Vilnius and Warsaw are both located inland. Furthermore, the role of private citizens in the outbreak of conflict would undoubtedly vary between the cities; in Vilnius, for example, the Lithuanian government has distributed a manual describing what role civilians can play in the event of war.

9. Suez City, Egypt

Suez City’s population of less than half a million makes it one of the smallest on this list. But as the southern gateway to the Suez Canal—through which almost a tenth of global trade transits—makes it disproportionately important to US national (and global) interests. The effects of any closure of the canal would be felt deeply across the world.

Suez City has seen conflict before. It was the site of the last major battle of the 1973 Yom Kippur War—when Israeli soldiers attacked the city but met with high casualties from the defending Egyptian forces. Even before that, when the Egyptian government nationalized the canal in 1956, it triggered a military crisis. While any future closure is seen as unlikely, an external military response would be expected. Former Defense Secretary James Mattis, while serving as a Marine general in command of US Central Command, acknowledged that the US would respond “diplomatically, economically, militarily” (emphasis added) to any attempt to shut the canal to international traffic. In such a scenario, Suez City would represent an important piece of key terrain.

10. Mogadishu, Somalia

Home to 2.5 million people, Mogadishu accounts for about one-quarter of Somalia’s population. In a country of chronic instability and economic underdevelopment, the drivers of both are on particularly sharp display in the capital city.

Perhaps Mogadishu’s most important contribution to this list is a notable incident in US military history that occurred there. The Battle of Mogadishu highlights remarkably well how the internal dynamics of a city can transform dramatically and quickly. The events that would become the subject of journalist Mark Bowden’s book Black Hawk Down and the subsequent film of the same name also demonstrate that the scope of traditional intelligence is woefully insufficient for urban environments. Current maps and an ability to track high-value enemy targets might be important, but so is developing a capacity to dynamically measure a range of other characteristics—like public sentiment toward friendly forces.

11. São Paulo and Rio de Janeiro, Brazil

Individually, São Paulo and Rio de Janeiro are each large cities (with populations of around twelve million and six and a half million, respectively), and each has substantial challenges and vulnerabilities—from São Paulo’s endemic water shortages to Rio de Janeiro’s high levels of violent crime. Both also struggle with the social and security implications of dramatic wealth disparities. But despite their city centers being hundreds of kilometers apart, they offer an example of a new phenomenon: the rise of the “mega-region.” As a United Nation study found, the divide separating the two cities now encompasses more than forty-three million people, and there is no clear line where the sprawl of either city ends.

Connectivity between people—combatants and noncombatants—in densely populated cities has long made them more complex operating environments than sparsely populated rural areas. But as cities connect, it makes each of them even more complex as a result. Specific military operations no longer reverberate on neighboring blocks or even the other side of a city, but across seamless expanses of populated regions.

So what should the US military do with a list like this? First, it should recognize it as a starting point—aimed at demonstrating the sheer diversity of cities’ physical features, social landscapes, and specific risks. Seeking to develop a comprehensive list of every city of concern and every potential contingency that could draw US forces into urban areas is a fool’s errand. But there is value in beginning a conversation, and the Defense Department—and its individual services—would be well served to develop lists like this one, so long as they treat them as dynamic documents. Doing so is vital in order to begin exploring important questions that will have very different answers in different cities. Some of the questions that pre-conflict analyses might consider include (but are certainly not limited to): How would the city be evacuated if needed? Where are the ideal locations to house internally displaced people? How would the city be defended? How would it be attacked? How would it be rebuilt? What needs to be protected inside the city? What are the city’s vital flows in and out?

To explore these questions, the military should consider creating city specialists to complement the work of country experts. War games that not only take into account a city’s unique features but are built around them should be planned and conducted. New intelligence methodologies should be fashioned and refined. Tools that help develop a picture of the system of systems that composes each city are necessary. If history is any guide, planners will not be afforded sufficient time to truly understand a city before the US military is called on to operate there. But there are steps that can be taken now to give our forces the best chance at succeeding when operating in a specific urban environment is required.

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 on Twitter: @SpencerGuard

John Amble is the editorial director of the Modern War Institute at West Point and Co-Director of the Urban Warfare Project . He is a military intelligence officer in the US Army Reserve and a veteran of the Iraq and Afghanistan wars. Follow him on Twitter: @johnamble

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, Department of Defense, or the US government.

Image credit: Tosin Toromade