Five hundred years ago, a world-spanning, decades-long war triggered a planet-wide apocalypse. Survivors from the warring countries had to cluster and work together to survive. Survivors were also constantly defending themselves from hordes of rogue monsters left over from the military efforts of one collapsed empire. After a decade of desperately fighting for survival, the apocalyptic conditions are ended, someone finds (literally overnight) the key to getting rid of all of the rogue monsters, and civilization starts to pick itself back up again. The battered survivors, who've been pretty traumatized by war and a near-constant state of siege and who've had to overcome former national boundaries anyway, are led by people who take this opportunity to found a unified world government in the hopes of ushering in permanent peace. They have distance travel and communication technology back within a few years, so the "world" part isn't much of an issue even as people re-disperse, and the surviving population was probably under a million.

It's been five hundred years. There have been a few minor rebellions, but nothing major and several of them were closer to waves of unrest than fighting. Weapons technology beyond the individual arm is heavily restricted, although the "everyone has to be able to fight to survive" culture has been idealized and lingered in a recreational arms-friendly culture like you see in parts of the US, albeit with more emphasis on hand weapons and less on firearms and without the inherent anti-government sentiment. Nobody's found or even imagined aliens; this world is all there is. There aren't any external threats to worry about, just internal.

What kind of military/peacekeeping/armed police forces might such a world be likely to have, and how large might they be (relative to the population)? Alternately, what kinds of political or social factors would drive the "need" end of the decision-making? For example: maintaining a large inventory of high-tech artillery seems unlikely because the maintenance costs are non-trivial and the visible benefit to society is very low. But having some large-scale weaponry is useful in the rare rebellion scenario-- how might a government decide what's "enough"?

I realize there's a range of answers, and a military police state will, of course, look different than a hippie utopia; the society is going to be somewhere in the middle and (for simplicity) bear a surface resemblance to a modern Western democracy. The reasoning behind answers is therefore especially appreciated so that I can decide where on the spectrum I should put the society and government policies in order to support both a civilian life that takes peace utterly for granted and an elite clique plotting coups using recreated mega weapons.

(I'm also willing to take "Your scenario is totally unbelievable from a societal perspective, and here's why", although that may result in follow-up questions later.)

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    $\begingroup$ "a world-spanning, decades-long war triggered a planet-wide apocalypse. ... After a decade of desperately fighting for survival, the apocalyptic conditions are ended ... They have distance travel and communication technology back within a few years," NO. Absolutely not. Civilization doesn't rebuild and repopulate nearly that fast. (Many Germany villages took a century to return to the same population as before the 30 Years War, and a technological society will take much longer to rebuild. $\endgroup$ – RonJohn Jul 25 '18 at 2:43
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    $\begingroup$ Sorry, I should be clear: the population is nowhere near rebuilding after a few years. But basic radio-level communication wasn't lost and there are a lot of reusable travel technologies that can be used and scavenged for part during the lengthy process of rebuilding an industrial base and population. The disaster in question left a lot of humans dead without damaging their surroundings, so raw (if imperfect) parts are common; think bioweapons. $\endgroup$ – Hufflehobbit Jul 25 '18 at 3:34
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    $\begingroup$ "But basic radio-level communication wasn't lost and ..." That's reasonable. But with so much depopulation, there's no need for a world government so soon after the mutant war ended. (The gaps between your cells of survivors is way too large. Nearby towns have to decide to band together into little states, and grow from there.) $\endgroup$ – RonJohn Jul 25 '18 at 4:17
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    $\begingroup$ A "peacekeeper" is different from a soldier-on-occupation-duty, so beware falling into that vocabulary trap. Peacekeepers are neutral observers and trust-builders, and police an already-agreed peace by former belligerents. Peacekeepers do not impose a peace on one or both sides - that's what occupation soldiers do. $\endgroup$ – user535733 Aug 17 '18 at 3:22

In the real world, the data varies just how many police you need to keep law and order within a population. This depends on the culture in question, and also on the kind of jobs the police are supposed to handle, and what other forces do.

  • The Chicago Police Department has roughly 400 police per 100,000 people. The New York City Police Department has roughly 500. The Los Angeles Police Department has roughly 300.
  • Berlin has roughly 660 police and non-officer employees per 100,000 people. The (greater) London Police has roughly 540.
  • Hong Kong has roughly 400 officers per 100,000 people.
  • The US routinely uses national guard units for tasks that would be handled by riot police in other countries. This could suggest that US police numbers are on the low end for the country.

Summarized, call it 500 "cops" per 100,000 inhabitants.

  • During the Cold War, industrialized countries had perhaps 1,000 active-duty soldiers per 100,000 inhabitants, give or take a few.

So for a ballpark, slash the number of "soldiers" by 90% to get the "peacekeepers." That would make them few enough that their numbers are lost in the variation of police figures.

Say that 15% or 20% of the police are "peacekeepers" with assault rifles, machine guns, light APCs, heavy trucks, and helicopters. Another 15% to 20% are "riot squads" with light APCs, water cannon, and also a few helicopters. The total of these forces is 150 to 200 per 100,000 inhabitants.

And a certain percentage of the "peacekeepers" have tracked IFVs and a few MBTs instead of wheeled APCs. One battalion in five? One in ten?

For every 5 million inhabitants of the world (the size of Denmark, or the Washington metro area) there is one "peacekeeper battalion combat team" with one armed scout car company, three APC-mounted rifle companies, and a mortar company, reinforced by a drone/helicopter aviation company, an engineer company, and a military intelligence company. There is also one "riot battalion" with half a dozen infantry companies, who have both rifles and riot shields/batons in their MRAPs.

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    $\begingroup$ Good post! Don´t forget that Armys also support in natural catastrophes nowadays. I´d guess you´d have to either keep the pioneer-battalions or ramp up the fire-brigade to make up for that. $\endgroup$ – Daniel Jul 25 '18 at 9:37
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    $\begingroup$ That is a very good point, how does the national guard play into these numbers $\endgroup$ – Andrey Jul 25 '18 at 13:55
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    $\begingroup$ @Andrey, if the NG is available for internal security in an emergency then one can risk having lower numbers of police. That means when one looks for a "normal level" of police, states with available NG are a bad example. Mostly it means I discounted the LAPD numbers and went closer to London. $\endgroup$ – o.m. Jul 25 '18 at 15:09

It depends on just how unified you mean when you say the world is unified.

If the world is very unified under one government, and there is no anti-government sentiment, they wouldn't need many weapons at all. You will still presumably have crime, and so will still need armed police. Presumably since firearms are uncommon, violent crime will be more common but less lethal. Criminals will have less to fear when accosting their victims, but will also be less able to kill each other when they fight amongst themselves.

So the average police officer will likely be about as well-armed as they are in real life. You will still have SWAT teams who are more heavily-armed, and perhaps an even more-heavily-armed unit for handling situations like Waco. But this unit would be just a few thousand people with armories all around the world. In a crisis, they would be flown to the nearest airport and would gather equipment at the nearest armory. You would not have a military.

If the world is not as unified, and instead the world government is something akin to the UN, you will still see lots of in-fighting. Local factions would still want all the weaponry they can get. The world government would probably want quite a bit as well so they can enforce their decisions.

I would say that the level of violence, and thus the amount of weaponry needed, in this world depends on exactly how unified they are. This would range from as violent as the real world, to much less violent both in military and criminal terms. A world government could much more effectively crack down on international crimes like drug smuggling and sex trafficking. But I can't see any world involving humans being devoid of violence.

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    $\begingroup$ Presumably since firearms are uncommon, violent crime will be more common but less lethal. Do you have any citations for that? All the examples I know show a different trend ... $\endgroup$ – Daniel Jul 25 '18 at 9:30
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    $\begingroup$ nationmaster.com/country-info/compare/United-Kingdom/… Murders are significantly lower in the UK, assaults, rapes, and total crime are higher in the UK. Some of the difference in murder rates is also because of how the UK counts murders compared with how the US counts murders. In the UK, a death is only counted as a murder once someone is convicted, no matter how obvious it was that it was murder. publications.parliament.uk/pa/cm199900/cmselect/cmhaff/95/… $\endgroup$ – Ryan_L Jul 25 '18 at 14:27
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    $\begingroup$ Having only 1 recognized world government is a little different than not having any places on the planet where law is poorly enforced. Imagine Brazil was the whole world. It has 1 government, but some areas police don't enter without military backup $\endgroup$ – Andrey Jul 25 '18 at 19:58

In name none whatsoever, but in reality what you'll have is various forces and agencies that whose official job is anything but as peacekeepers. These groups would be highly trained and tasked with missions like "monitoring and containment of predator populations in sector 11" and a whole host of other tasks that have some things in common:

  1. they require physical prowess.

  2. they require weapons and training in how to use them.

  3. they appear separate but fall under a single command structure that is beyond reproach.

  4. the tasks and the training needed to complete them are cross applicable to putting down rogue humans at need.

What you have is a reaction force that is never called an enforcement arm, never considered a peacekeeping force but can be called upon to fill those roles at need.


You need to have sufficient force to defeat any likely foe (or at least delay them long enough to build up the rest of the force you need; the US didn't start WW2 with a big enough fleet to defeat Japan, but that doesn't mean the fleet they had was unimportant). Threats basically come in two flavors: weak-but-angry groups merging, and strong-but-friendly groups turning against you.

In the weak-but-angry category you have things like criminals, big corporations, politicians - people who you know already might have a motive to start fighting one another. What they lack is a standing military force, so your job is to stop them from accumulating people and equipment. How large your peacekeeping force needs to be to defeat these groups depends on how well your intelligence and law enforcement are at finding them while they're still small.

In the strong-but-friendly category you have things like standing armies of constituent nation-states and your own peacekeeping forces. The threat here is someone like a rogue general or politician using these troops to further their plans, or selling them to someone else for that purpose. How large your peacekeeping force needs to be to defeat these groups depends on how large they are and how they're structured. (Larger, monolithic groups with less oversight are bad. Smaller groups that you can keep an eye on will help limit the damage if one turns against you.)

In short: the better your law enforcement is at finding criminal conspiracies, the better your political system is at ensuring oversight over your military, and the smaller your allied militaries are, the smaller your peacekeeping force needs to be. This is because your goal is to quell problems before they get to the point where you need a large army.

As for how a government would actually decide - it's typical for a government to have at least one agency responsible for hypothesizing about, researching, simulating, and ultimately drawing up plans for all manner of situations. (In the US, this is part of what the FBI does, and there are other agencies who do their own disaster planning.) They would be responsible for looking at the condition of the world and deciding what the likely minimum level of strength is.

Then you have the inevitable tension between planners who want a margin of error and politicians who don't want to spend the money to get it. However, the starting point is simply "what's the worst problem that we foresee, and what will we need to stop it?" with a dose of "what are acceptable losses in the event we're wrong?" and "how much are we willing to spend to minimize risk?".

  • $\begingroup$ The threat here is someone like a rogue general or politician using these troops to further their plans, or selling them to someone else for that purpose. How large your peacekeeping force needs to be to defeat these groups depends on how large they are and how they're structured. - That argument bites itself in the tail. The larger the force , the larger the tread from it going rouge. Would be better countered by having flat hierarchy and lots of Chinese walls between individual units $\endgroup$ – Daniel Jul 25 '18 at 9:34
  • $\begingroup$ @Daniel "Watching the watchmen" is always going to be a non-trivial difficulty in a situation like this. As you say, the best idea is to keep them divided into manageable chunks. The key is that the peacekeepers as a whole need to be strong enough to contain one of those chunks (preferably several) should the need arise. $\endgroup$ – Cadence Jul 25 '18 at 13:51

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