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defense If the wall is particularly thick, it could be used as a platform for placing defensive weapons onto for a better line of sight against incoming missiles, bombs, aircraft, and whatever other threats that a wall doesn't counter. Put a large amount of CIWS guns along the wall and you could have decent protection against air targets. You could also ...


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It's not really about the walls, it's about the gates. The only way to get through your wall into the city is via the handful of carefully planned and well-defended gates. These serve as natural choke points that make it easier to defend against a ground assault. It also makes it far more difficult for spies, smugglers, or enemy sympathizers to sneak into ...


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Insurgents using snipers. https://en.wikipedia.org/wiki/Sniper_Alley The wall doesn't even need to be bulletproof, so long as the snipers can't see their targets they can't shoot.


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COVID-32: This time it's 95% lethal. Nuff said, really. If you'd like more, Fortress WA may still be holding out somewhat against Omicron, and China may keep it out, but if you absolutely positively don't want to all die of a deadly disease, walls at the city level might be your better option.


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I'm not certain about the conditions which might make building walls around cities necessary or desirable, but I can say that with modern conditions of relative wealth and ease of construction compared to premodern societies building walls around cities would be comparatively easy. I'm not certain that modern people would be okay with gates where every road ...


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Protection for citizens who might wander into defensive zones. Robotic drones attack anything that moves in certain geographic areas. The drones limit their attacks using a GPS equivalent, but any hapless citizen who wanders into a "free attack" territory meets a bad end. Inhabited areas surround themselves with walls not to keep anything out, but ...


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A city which has been built in the middle of the sea. Walls were built to protect the people from tides. Pumps removed the water so that they could have dry land. Of course, a 'sea-city' would be expensive, hard to build and probably not worth it. But, you could have an amazing tourist industry


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Dangerous Animals The animals we have now on Earth are largely non-threatening to humans and do not intentionally prey on us for the most part. However, a different setting could have a different species occupy the top of the food chain and actively hunt humans, so that humans need walls around their cities to prevent these animals from getting inside. ...


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The purpose of these walls should be city defense. Defense against guerrilla warfare is OK, but I would prefer the walls to also be able to defend against large-scale military assaults. People are still using all the techniques of modern warfare; not just a wall of infantry. Firstly, it wasn't tagged reality check, but I think you need one. Walls are ...


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An Escape from New York Scenario If you haven't seen this classic movie, the premise is that the people of the USA built a wall around New York to keep the crazies and the criminals in. So it is a wall for defense, just not for defense of the city, actually the defense of the rest of us. They did something similar with Los Angeles in the sequel. If we did ...


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In the OP you mentioned that rockets are contemporary warfare, but airborne attacks (from a bomber or missile etc.) still carry warheads or other bombs so walls are kind of useless if you can fly over them. Unless you want to dial the warfare back to preindustrial I don't think walls would be effective for any warfare related reason. However, walls are ...


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There is an big wall around an entire country in our current world 2022. It is a MASSIVE wall, but it's invisible. It's sole purpose is to keep citizens in and attackers out. It is not a wall in the classical sense, but it essentially functions as a wall and that makes it a wall. Of course I'm speaking of the great chinese wall. The digital one, the great ...


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Not On Earth Your city is a habitat on a planet that dont have a naturally survivable atmosphere, so a barrier of either metal, glass, or even some kind of energy shield (you didn't specify which part of 21st century, we still got 80 year ahead of us) is necessary to contain oxygen and shield cosmos radiation. In this case, you can even have some kind of ...


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Political oppression Source: Wikimedia Commons The Berlin Wall encircled West Berlin from 1961 to 1989. The official aim of the Berlin Wall was to protect the city against fascist agitators coming to stoke unrest. Does that count as city defence? Of course, the real aim of the Berlin Wall was that residents of the German Democratic Republic could not get ...


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Monsters or Zombies I cannot imagine there are many scenarios that call for giant walls around civilian populations. So the question is basically, what kind of threat would change the world enough to make nations build walls around their cities. It would have to be an enemy. An enemy that can operate freely across large amounts of a nation without serious ...


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Lots of low grade military action. Steel walls are already common in cities where crime is high. Having steel shutters over vulnerable things is normal and expected in society. This is enough to deter casual vandalism and small calibre fire. Some nations take it further. Israeli buildings are often built with steel reinforced concrete, because of the risk ...


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I can think of one city on particular that remains walled to some considerable degree to this day, and that is Jerusalem. Jerusalem has its main, infamous wall for the primary purpose of formalizing a boundary between the Palestinian and Israeli-controlled parts of the city. You could also reimagine the many checkpoints around Jerusalem as walls, which gives ...


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Rising sea levels A coastal city-state, like Monaco or Singapore, would be extremely vulnerable to global warming and sea level changes, and the world economy would have a strong interest in protecting the financial sector in those states. So it would make sense for Monaco and Singapore to invest in sea walls. Other cities with important waterways and ...


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Well-connected military contractors plus scare campaign Let's have a quick look at what putting a wall around a city will do: Cost the government a ton of money that will be unavailable from funding combatant units and equipment. (Note that only an affluent society will have enough money available for this project at all.) Require a cleared zone either ...


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High crime rates, high gun ownership, drug lords operate without effective intervention, the continual defunctionalizing of the American police forces, and the criminal/quasi-legal terrorist organizations concentrate in particular cities, necessitating civilized society to defend itself within 'safe cities'. I would actually extend this to particular regions ...


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A Poorly Defined Civil War Zone There are plenty of reasons to build a wall in a modern context (segregation, immigration control, socio-economics, etc), but when it comes to repelling an attack against large-scale military assaults... they are pretty much useless. So to answer the question, we need to take some liberty in defining what a large-scale ...


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Prolonged World War 3, lasting decades if not generations, assuming the nuclear warheads don't already wipe us out and somehow all the governments remain intact. Even in middle ages walls don't typically enclose cities, they enclose keeps. Wealthier lords might build a second wall to enclose the urban class, but most of the population remained outside. This ...


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Fishing rights The fishing here is very very good due to current upwelling like around the Galapagos Island. (This means that the island would soon enough turn into a haven for sea birds. Grasses would soon arrive.) Thus, the country that not only claims it, but successfully defends it, gets a large bounty of fish (and therefore wealth).


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Singapore has a single, distant oceanic territory that's just a lighthouse (We have lots of fun geopolitics with lighthouses and our bigger neighbour. We run a lighthouse on someone else's land. Another useful point of reference would be Hans Island, site of the Whisky War In the age of sail colonial powers tended to plant their flags on anything that didn't ...


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Scientific site Despite its lack of natural resource, the island itself is (surprisingly) located miraculously well. It has lots of potential for scientific research. I was thinking astronomy (predictable weather, unobstructed view down to zero-degree elevation) but it could be something else more creative. It can also be used for testing purposes in ...


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How could you NOT want to occupy this island and build a naval base there? Your naval operations in the ocean, especially close to the enemy coast, will benefit greatly if they don't have to sail all the way back the the homeland for re-supply and/or repairs. They go to the base on the island instead, which shaves about 3 weeks off the turnaround trip. This ...


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Piracy and trade The island can be stocked with supplies and fortifications by whichever nation uses it. This gives you a massive advantage in trade and piracy, allowing you a larger cut in resources and supplies. Imagine you are a trading vessel. If you anger the authorities or you run short of supplies you can go to this island. Imagine you are a pirate ...


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The British empire did it with almost any rock emerging from the surface of the sea: Saint Helena, Falkland, Ferdinandea island, Tristan da Cunha are just a few examples. Ferdinandea was just a clump of freshly spewed lava when the disputes on its ownership started, and were suspended as soon as the water retook possession of it. Having an outpost in the sea ...


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