Editor's note: The original version of this article published on Dec. 28 misidentified David Scott.

ORLANDO, Fla. — US land forces will eventually find themselves locked in fights within huge, dense urban environments where skyscrapers tower over enormous shanty towns, and these troops need more realistic training to operate within these future megacities, a US Marine general is warning.

"I've trained in every environment, jungle, the desert, the mountains, cold weather, but I've never really trained well in an urban environment," said Brig. Gen. Julian Alford, the Marine Corps Warfighting Laboratory commander, earlier this month at the Interservice/Industry Training, Simulation and Education Conference (I/ITSEC) in Orlando, Florida.

For him, that's a problem because "the first time I ever dropped a bomb, shot a rocket, threw a grenade, killed a person was for real in an urban environment," he said. "That should never happen again."

Alford said, "We have to figure out how we are going to fight in this environment because the forecast tells us that people all over the world are migrating, they are migrating toward cities."

Alford is tasked to try to forecast where the Marine Corps will fight in the future, write concepts and then wargame those concepts in order to feed science and technology development. The one-star general asked industry participants at I/ITSEC to help coming up with ways to prepare troops to better fight in an environment that is becoming a reality.

"We are going to have these megacities that are ringed with these shanty towns and we are going to fight there because it will be the people who are uneducated, unemployed, the young men who are not married and they are mad about their lot in life," Alford said.

"We talk about the three-block war, but we are moving quickly to the four-floor war," he added. "We are going to be on the top floor of a skyscraper . . . evacuating civilians and helping people. The middle floor, we might be detaining really bad people that we've caught. On the first floor we will be down there killing them. … At the same time they will be getting away through the subway or subterrain. How do we train to fight that? Because it is coming, that fight right there is coming I do believe with all my heart."

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Simulating such training isn't about replicating counter-insurgency maneuvers. "One of the problems I've had when I start to talk about fighting in an urban area, people immediately go to a COIN [counter-insurgency] fight. I'm talking about a high-end, wide-open, peer-on-peer fight," Alford said.

The training developed to simulate "some of the most difficult fighting on Earth," Alford said, also needs to be designed to refine not just the skills of individuals but entire units working together.

Marine Corps Commandant Robert Neller added it's not easy to just go and build something that would simulate a megacity. "We can't afford to go out and build a 20-story skyscraper at Twentynine Palms or stack shipping containers that high, we are just not going to do that," he said. "So how do you get the sensation or at least make you go through the mental calculus of trying to figure out how you are going to do that?"

One way to get at training in such a demanding future battlefield is through augmented virtual reality, Maj. Gen. James Lukeman, the commander for Marine Corps Training and Education Command, said at the conference. "That type of technology, you could go into a building and any building could become an augmented facility at that point because you are able to augment the building with those types of battlefield effects," he said, adding, "some of that technology has great promise in training small units."

Augmented reality shows a real landscape and other troops but can, using head-mounted displays, superimpose or overlay virtual reality images and effects such as vehicles, explosions and aircraft dropping bombs.

David Scott, Lockheed Martin's business development vice president for training and logistics solutions, said there are ways to use augmented and virtual reality to simulate training in megacities. "We are able to build big cities virtually," he said, designed to encounter the full population or virtual adversaries.

Another way to increase the effectiveness of training as a unit in an environment like a megacity is using simulators that are connected. Lockheed's combat convoy simulator and also its F-35 simulator can link up with other simulators to train as a unit or a squadron, for instance.

Scott said a big growth area in the defense training industry is connecting virtual and augmented training through a network. Now a larger number of simulators can work in tandem and put troops in training into constructive environments where it's not just about shooting but assessing dynamic situations, interacting with the population and judging what actions to take.

Preparing to fight in megacities is also something the Army has been tackling for several years.

In the Army's 2014 Unified Quest, an annual wargaming exercise, the service imagined the battlefield of the future as a flooded megacity, where the enemy is hard to spot, danger lurks below ground and in skyscrapers and military operations will be complicated to execute.

At that time the service counted 24 megacities worldwide today and says rapid urbanization will ensure they're far more prevalent by 2035. Cities are no longer something you move through or easily contain. As those who fought in places like Baghdad know, cities can swallow units whole and friends and enemies look the same.

The Army Training and Doctrine Command's "Mad Scientist" initiative will soon again tackle operating in megacities. In an April event next year, the Army will assess the challenges of fighting in megacities, according to Kira Hutchinson, TRADOC's director of intelligence and engagement.