Yes, cities are getting bigger. Big enough to add the prefix "mega" to many of them. So opportunities to fight in cities increase every year. The battle for Mosul shows how difficult it can be:
The battle for Mosul represents the future of warfare—and it wasn’t pretty for America’s allies. A ragtag army of a few thousand Islamic State fighters managed to hold the city for months against some 100,000 U.S.-backed Iraqi security forces. The ISIS fighters communicated via social media and were armed with crude explosive devices and drones available at Wal-Mart . In the end the rebel fighters were dislodged, but not before an estimated 7,000 people were killed and another 22,000 wounded.
U.S. commanders ought to imagine how they would handle a similar environment. Future American conflicts will not be waged in the caves or craggy mountaintops of Afghanistan, much less the open deserts of Iraq or the jungles of Vietnam. They will be fought in cities—dense, often overpopulated and full of obstacles: labyrinthine apartment blocks, concealed tunnels, panicking civilians. The enemy will be highly networked and integrated into his surroundings. America’s next war will be the 1993 Battle of Mogadishu on steroids.
If the Battle of Mogadishu on steroids is the template, our enemies won't long survive given that our kill ratio was as high as 25:1 in that battle.
While opportunities for battles in cities will grow, should the Army enter those cities? I think we should avoid them, and there are few reasons to violate that avoidance.
Liberating one of our own cities is surely a good reason to fight in a city. The war is going rather poorly if that is the case, you must admit.
But short of that, what are the reasons to take an enemy city rather than push past it to let the defenders wither on the vine while our army seeks to defeat the enemy army in the field?
I'm not persuaded that the Battle for Mosul is the model in that situation.
If an enemy army defends such a city, unlike ISIL it will be reliant on logistics and supplies that cannot be extracted from a civilian population and a local Wal-Mart (and no, explosives are not available at a Wal-Mart) the way ISIL could sustain itself. Bypass and seal off the city and let that army wither on the vine. It's their city, let them feed their own people left in it.
If we have to take an enemy city, try to do it fast the way we bounced Baghdad in 2003 with the Thunder Run by 3rd Infantry and the Marines to the east. Could we really afford to take 8 months to take an enemy-held city in the path of our army? Imagine the Allied offensive grinding to a halt for 8 months to carefully (to avoid friendly civilian casualties) take Paris in summer 1944 while the rest of the German army retreated east?
And why take that much care to avoid enemy civilians if the price of that care is to prolong enemy resistance and so tie down a lot of our troops that will have the effect of prolonging the war?
All things being equal, I'd rather avoid fighting in cities. If I have to, I'd rather just take the militarily significant portion and leave the rest. And overall, I'd rather get it over fast. (Consider whether there would be fewer casualties in a fast victory than in a prolonged battle that kills civilians at a lower rate--but for a much longer period of time.)
Granted, the Mosul model applies to liberating one of your own cities that an irregular enemy had more than two years to prepare for a siege. Like Mosul. But is that really the circumstance we will face in other potential city battles?
Mind you, we should prepare for them, although I wouldn't create combat brigades focused on city combat. The Marines who naturally prepare to assault defended shores might find assaulting a city where their boots don't get soaked a comparative joy. I'd make them the lead force for city combat.
But I'd also have an Army urban warfare school just as their are schools for cold weather, jungle warfare, armored warfare, airborne assault, and anything else, really.
And I'd prepare Army combat engineers to fight in cities so they can leverage Army units prepared when needed for urban combat led by officers and senior NCOs who have attended an urban warfare school.
But as a matter of course, I'd try to keep the Army in the open and moving rather than bogged down in an 8-month campaign to take a city block by block.
