Top Army leaders have said recently that several factors are fundamentally changing the character, but not the nature of war.

While one of the major drivers is technology, the Army's Chief of Staff, Gen. Mark Milley, described another notion that some in the Pentagon have mentioned: the dense urbanization of global populations.

This has huge implications for armies and specifically the U.S. Army, he said at an event hosted by the Atlantic Council on May 4 in Washington, D.C.

Here’s how this trend breaks down in the next 30 or so years: Milley described a current global population of around 6 billion people. By 2050, that number is projected to grow to 8 billion people, of which 85-90 percent will live in highly dense, complex urban areas.

Moreover, Milley discussed megacities, defined as cities with populations over 10 million people — Seoul, South Korea; Tokyo; and Mexico City, for example. Today there are 10 to 15 of these cities, while in 2050 there might be over 50.

On top of these megacities, there will be even more cities with populations of 2 million to 5 million.

So what does this mean for the Army?

"It’s highly probable that the military forces armed conflict will occur in highly dense urban complex terrain, physical terrain," he said.

The problem?

"The U.S. Army has been optimized to fight in rural terrain, to fight in plains of northern Europe, North America and deserts in the Middle East," he added, which has implications for how they organize and equip themselves.

Other implications for urban battle mean that equipment such as tank barrels or UAV wingspans will have to be adjusted. Command and control and communication could be challenging with reinforced concrete that could interfere with signals.

"As we go forward," Milley said, "we’re probably going to have to shift gears significantly in the coming decade or so to optimize the Army," as well as all land forces to include the Marines, to operate successfully in highly dense, complex urban areas.

2008 was the first time in history that more than half the global population lived in an urban area, so by 2030, close to 60 percent of the population will live in an urban area, Lt. Gen. Robert Ashley, the Army’s deputy chief of staff for intelligence, said during a conference in September 2016. As such, he said the more he thinks about intelligence, surveillance and reconnaissance, he is going to need a swarming capability — something unmanned and small to be able to operate in these urban environments. They also must be expendable and cheap, he added.

This also has implications for other forces such as the Air Force, which conducts air strikes from above, made significantly more complicated in urban environments. However, some Air Force officials have touted the highly adaptable capabilities in some of their platforms and innovation of airman.

The Air Force’s MQ-9 Reaper drones are conducting urban close air support, a very difficult task. First lieutenants figured out how to do this in Libya recently, Lt. Gen.

Mark Nowland, deputy chief of staff for operations for the Air Force,

said in a recent speech. Describing a scenario, he said members of the Islamic State group in Sirte, Libya had snipers atop big, tall buildings and snipers sitting in windows. Using a two-ship, one buddy lase approach, which provides a precise laser spot for laser guided bombs, the platform would lock on after launch, provide a thermobaric effect, hit the window, and kill the sniper in the window without taking down the building while supporting the ground force.

In fact, Milley said current operations are providing "previews, the movie trailers of future conflict in my opinion, in Mosul, Fallujah, Aleppo, pick your urban area," but cautioned that Mosul is not even a neighborhood in Seoul, a so-called megacity.

While the Army and DoD are taking lessons from the fight in Mosul, Milley said it is incumbent upon him, leaders, the Army and DoD to learn these lessons for future conflicts.

The Army will have to learn not to operate with large logistical mountains right behind them, Milley said. Rather, they must untether themselves from this "umbilical cord," fight in smaller groups, be able to fight and survive in environments that will be highly lethal, move constantly, every 2, 3, 4 hours just to survive, and produce resupply items such as fuel and water themselves forward.

"The fact of the matter is I don’t think we’re going to have the luxury of having this massive mountain of logistics behind us in future higher end, higher intensity conflict," he said.

The Army is looking to address this through initiatives such as its demand reduction strategy, both trying to reduce it’s critical logistical needs while looking at more efficient methods of delivers and production of these needs to forward deployed units.

Mark Pomerleau is a reporter for C4ISRNET, covering information warfare and cyberspace.