How to survive a siege for fifty years?

Question

A long and costly war is finally coming to a close. The rebels are losing territory fast and only have rolling hills to guard their last city. According to the scouts, the imperialist regime is about 2 weeks away and advancing fast. The rebels are outnumbered 3:1. The last city has a fighting force of about 10,000 with a civilian count of 200,000. Backed against the coastline, and with no mountains, what can the rebels do to defend their homeland?

They have scorched the surrounding area, leaving only ruined settlements and burnt fields between them and the opposing force. The rebel's capital city has basic walls but is entirely self-sustainable if it needs to be completely sealed. The rebels have strong public support, while the regime is already at arms with its own civilians. The rebels have been preparing for this war by stockpiling weapons, gear, and resources for generations. They know they can't win the war by offense alone and have resorted to waiting the empire out. The rebels hope for the empire to fracture within 50 years, either from the royals dying or from lack of resources. I have prepared a list of their resources:

Resources:

• 500 sq. mile city
• Extensive farms, forges, mines inside the city
• Endless materials (wool, lumber, stone, etc.) from the self-sustaining city
• Roman-level of technology (100 AD)
• Strong public support
• Immunity to disease (handwave)

Planetary Information:

• Slow rotation (1 week day, 1 week night)
• Strong winds along the coast, reduced but still windy inland
• No mountains in the nearby area

Clarification:

• The rebels have the super-windy coastlines to their left, with rolling hills above, below, and to their right

What can the rebels do to prepare and survive the 50-year siege, if at all?

Answer 1

The rebels are doomed

Let's assume that the 500 square mile city is a rectangle 20 miles by 25 miles, with one of the long sides covered by the sea. Assuming that the advancing force does not have any naval assets (more on that later) then there are 65 miles of wall to defend. The 10,000 defenders will have trouble even monitoring a wall this long constantly, especially during nights that last an entire week. The attackers can feint and move around, finally committing to battle where they want and overwhelm the thinly spread defenders. Even if the defenders do manage to detect the approach, and have a centrally located reserve, the odds are that the reserve will need to move over 10 miles to respond to an attack, which will have achieved a break-in by that time.

The rebels' only hope of short term salvation is to scorch the land for a weeks' travel in all directions, so the attacking army will need to spend some time building up its supply lines and infrastructure before it can bring its troops close. However, trying to sterilize the ground in all directions for a week is a task that is probably beyond the resources and organisational abilities of the rebels regardless. Even if they need to take 10 years to do so, the imperials can slowly rebuild supply outposts and supporting farms along the route to the rebel city. Over the time frame of a few years the imperials would also build a port, if they do not already have one, and mount attacks from the sea on the city and its fishing fleets, because...

200,000 people in an area of 500 square miles will have difficulty feeding themselves over 50 years without external resupply. This is 400 people per square mile - even assuming that most structures have rooftop gardens, this is close to the limits of primitive agriculture. All available area would be needed for crops, protein will need to come from the (vulnerable to Imperial attack) fishing fleet. Given that food must take top priority, there will be limited space left to raise animals or crops for other purposes, making cotton, wool, thatching material, lumber and leather high value commodities that it would not be terribly feasible to stockpile 50 years in advance.

One note on the subject of the rebels stockpiling resources for generations in advance. The ability to stockpile resources requires that they have a consistent surplus of wealth each year (on average) and the ability to store this wealth in a form that will not deteriorate. (Let's ignore the fact that people who are consistently getting more wealthy for generations are doing pretty well and have little reason to rebel en masse.) Most of the resources that the city will need on an ongoing basis are perishable. The most useful non-perishable resource to stockpile would be gold or other valuables that could be used (via a blockade running fleet) to buy critical supplies from elsewhere. However, supply by sea against an enemy of superior strength is a chancy business at the best of times even with relatively modern technology - the British pulled it off in World War II but they had a very strong fleet and it was still a close-run thing.

Answer 2

A generation is about 20-30 years so that's about two generations!!!! Ill answer your question with a real life equivalent the siege of Candia .....it was in mid 1600s so may be a "bit" to late for your needs. The siege of Candia lasted so long because Venice had allies who were willing to supply the city for as long as they needed which was 22 years till the city fell. Venice also constantly cut off ottoman Naval supply lines so they couldn't quickly supply. If your supplies take 8 months to get ready and shipped to your siege your siege is gonna take a bit of time (exaggeration).The ottomans also failed to completely block off the port so supplies were getting into the garrison. What do we learn from this?

1. Have a way for supplies to get in from the outside
2. Have allies
3. Cut of enemy supply lines repeatable over and over again

So the answer is simple control the seas for your rebels is practically the only way they hold out as long as supplies can get in the city then you can last a bit.

Answer 3

This is a Frame Challenge

The size of your wall and a 50-year siege are unbelievable. Here's why:

The Wall

Assuming a perfect circle, your wall's length is 79.3 miles. The density of your defense, if evenly spread out, is but one every 42 feet. That sounds like a lot, but it really isn't, especially when most guards are doubled up (now it's every 84 feet) and you have gate and watch tower emplacements taking some of the troops. It gets even worse when you realize that, at best, only 50% of your troops can be employed at one time (at all other times they're sleeping, eating, maintaining equipment, training...). But for the sake of comparison, let's stick with the 1:42 ratio.

Let's compare this to the Xi'an City Wall in China. That wall is only 8.7 miles long. Now let's think about population:

Xian lies some 600 miles south-west of Beijing, indeed it is the furthest west of all the major cities in China. But it was the first capital of the unified China, and in the Han dynasty (206 BC to AD 220) it had around a million inhabitants, and vied with Rome for the being the biggest city in the world. Later in the Tang dynasty (AD 600 – 900) it became if anything even bigger. (Source)

For convenience, let's stick with one million people and use your ratio of 1:20 for the fighters. That's 50,000 fighters on a 8.7 mile wall for an average of one fighter every 0.92 feet. A real-world example suggests you're understaffed for that wall by about 4,565%.

As designed, a good distraction would trivially open up a large enough hole in the wall's defenses to let an entire army through by climbing the wall before the nature of the distraction was understood. And the invading army could be better prepared to march across all that farmland than the wall's defenders.

Worse, you can't increase the population because you're trying to keep the population self-sufficient. 5X the population means 5X the necessary resources, most notably farmland. The more you try to fix the problem, the worse the problem gets.

The Siege

Let's examine the longest known siege (as a single effort) in human history: the Siege of Candia. That siege was about 20 years long and was fought between two sea powers, so some supplies could get through (support from sympathetic nations). The two nations, the Ottomans and the Venetians, were quite evenly matched in the beginning. Please note that sympathetic support — that's the practical equivalent of a self-sustaining city.

One thing the Ottomans couldn't do to the Venetians was undermine their fortifications. Keep in mind, the siege was primarily naval (Venice being what it is). Even a 20 year siege is more than enough time to simply dig tunnels under the wall starting from a far enough distance away that the defenders wouldn't notice the effort and couldn't do anything about it. But that's not the only problem.

That Wiki page ends with an interesting note. The Venetians planned, prepared, but did not execute biological warfare. Simply, they created a goo from the spleens of plague victims and planed to, basically, fling the goo at the Ottomans. Such a plan would work wonders against your city. In other words, whatever solutions are presented to you here — I'm pretty sure I can come up with a reasonable way to circumvent them and end the siege much, much sooner. When George S. Patton first encountered the French Maginot Line, he said:

This is a first-class case of man's monument to stupidity!

But it's the version from the 1970 film Patton that we're most familiar with:

Fixed fortifications are monuments to the stupidity of man. If mountain ranges and oceans can be overcome, then anything built by man can be overcome.

50 Years of Self-Sustaining City...

Sympathetic supplies means that natural problems in one location are offset by bounty in another. You don't have that privilege. You're assuming that for 50 years you have no drought, no disease (of people, plants, or animals... I know that you're handwaving this), that your material resources (minerals, lumber, stone, etc.) don't run out, and that people critical to the operation of the defense don't grow old and die. It also assumes that at the end of 50 years you don't have a population that's closer to 500,000, which would strain the resources of the original city 50 years earlier (a lot). That might seem to solve your wall manpower problem, but your city wasn't designed to feed or supply that many.

Fifty years is a whomping long time. It's not just a lifetime, it's several generations.

Conclusion

It's certainly true that you can craft a 50 year siege, but methinks that asking how to do it is irrelevant because realistically it is unlikely at best, impossible at worst. Presented with any answer to your question, I'm confident I can present a reasonable counter-argument as to why the siege would not last 50 years. Therefore, you're not really asking for a practical solution but a reasonable rationalization.

And at that point the question becomes too story-based, because we're helping you tell your story rather than answer a subjective question. Huh, after writing all this, I probably should have voted to close the question and requested that you clarify the circumstances of the siege and turn it into a reality-check question. In other words, I suspect I should have expected you to tell us how you wanted the siege to go, and we'd tell you if it was consistent with the rules of your world.

Answer 4

Sounds like you need to find not just ways to withstand it, but to prolong the siege.

Sounds like your city is already self-sustaining with "extensive farms" and "endless materials" inside the city. If there are no food or material constraints, then the siege can last indefinitely as the general purpose of a siege is to cripple the population such that they have no choice but to surrender.

Which then begs the question of the purpose of the siege - why does the Enemy not assault the city?

Finding the answer to this question will answer yours: you need to continually prevent the Enemy from assaulting you as doing so keeps the siege alive and prevents a wipeout.

There are several possible reasons:

1. Perhaps an assault is too costly to the Enemy, and they cannot afford the loss in men and equipment. Therefore, you need to continually work to maintain this advantage. Keep training your men, keep building your walls higher and higher with your infinite materials.
2. Perhaps it is not politically expedient to wipe you out. Keep this reason alive - keep sending messages to reinforce sympathy for your cause to prolong the siege.
3. Perhaps there is something in your city that the Enemy wants, which would be destroyed if they attack you. In this case, protect this, or hide it, and prolong the siege as long as possible by constantly letting them know you would destroy it if they attack. Reinforce this with a robust intelligence network to eliminate spies and layered defences to make it hard to obtain this item.

It is a curious situation, because another cause to end the siege would simply be surrender by exhaustion. For 50 years, people would be born and live their life in such a siege, so constantly persuading your own people of the worth of your Rebel cause will also need to be a priority - lest a faction of Sympathisers convinces your own forces and population to defect or overthrow you.

Answer 5

They won't survive.

If they do not have any outside allies relieving the siege they are doomed.

The attacking force would probably take their sweet time to win, but if this is indeed the rebel's final stand then that's it. The attackers would be "just" need to dig a moat around the city (in sufficient distance of course) and be done with it.

Nobody in, nobody out (except for over the sea, but then where?) and a minimal amount of guarding would be needed.

Leave it to the townsfolk to get rid of the enforced quarantine by disposing the rebel leaders, with the current pandemic we see how much even a loud minority gets displeased with only a few weeks of quarantine.

If you need to get a hold of the city sooner and are not to squeamish about the how, there is always gas:

You'd have to record the wind patterns around the place, but I guess they are quite predictable with the long day/night cycle.

With the given level of technology there are quite a few possibilities: Burn sulfur and you get nice clouds of sulfuric acid from the sulfur oxide and ambient humidity to name one.

Answer 6

50 years seems awfully long with roman age like technology. As mentioned in other answers, area is also huge for such a small garrison to patrol and hold. With such wide area to flank the enemy, this doesn't seem feasible.

You mentioned the rebels do have access to a coastline. The only way I can think of, the rebels are being supplied by a long time enemy of the imperials, something like French and British Empire rivarly.

"Others" that supply rebels do it only because they are a nuisance to imperials and pose a threat as a landing site for "Others".

Assault might be just a little bit too costly in life and resources for the Imperials, who need to focus their attention on other borders. But they have the same plan as the "others" do for them - waste their resources. So they dig up to prevent rebels from attacking (kinda like WW1 scenario), and use the siege as a training grounds for the troops.

But the reality is, if the imperials were really on it - no matter how well supplied they might be, 50 years of prolonged barrage from catapults (known 4th century BC) and soldiers will turn the city to dust.

Answer 7

As discussed in the other answers your current plan is not viable.

You can make this work though by having the last city be on an island in the middle of a very large lake.

The rebels destroyed all docks and boats on the outer shore of the lake before retreating.

They can smuggle in supplies over the lake and also use it for fishing to help sustain their population. This also means they don't need to defend all the wall - they just need to keep naval superiority over the water.

(One reason to use a lake rather than the ocean is it makes it harder for the attackers to bring in a fleet).

Have the island surrounded by rocks and cliffs, making it very hard for enemy boats to sneak across at night. You could even have bioluminescent algae in the water that glows on contact if you wanted to make it even harder for sneak attacks. (The locals would know tricks for avoiding algae or not disturbing it so they can sneak around in small boats).

The enemy would try and build new ships and docks - the defenders would destroy them from the sea in surprise attacks.

The enemy eventually could try and bring a new fleet in over land. You'd need to deal with that as well.

Answer 8

100 years war not 50 years siege.

A city being under continuous siege for many many years doesn't really have historical president but long running wars do, the 100 years war comes to mind.

Cost What you have to remember is that a siege is a very expensive and costly thing, you have to feed and pay and supply 1000s of men. Medieval economies are very impoverished and close to starvation as it is. It is a huge cost to maintain such an army, there would have to be a huge pressure to either assault and take the city right away or abandon the siege.

Seasonality In ancient times there was a concept of campaigning seasons. Good times of the year for war. When the populations isn't planting or harvesting crops, so there is lots of spare manpower. When the spring rains have stopped or the autumn ones haven't begun yet so the roads are not a swamp and supplies can be moved to supply the army. It would be rare and especially hard to maintain a siege year round.

What would more likely happen A much smaller city say 1/10th the area and population that counts on some amount of smuggling and external supply, from allies or other empires that just want to give this empire a hard time, to stay fed and supplied. The smuggling / blockade running / smuggling is helped by the long nights. The empire sends raiders to the surrounding land regularly but only for a few months a year actually sends a large assault army, and mounts a year round siege for a 2 years of the 50. The rebellious city is a nuisance but is not worth enough to pay the cost of a massive multi year siege.

Impacts of 1week night 1 week day

Extremes temperature variations. In the morning its cold out but it warms up as the sun rises and stays up then in the afternoon and evening it starts to cool down. If the sun stayed up for 7 times longer we would expect vastly hotter mid days and vastly colder midnights. In ancient times they had far fewer resources to deal with temperature extremes. It might well be true in a Day night 14x24 hour cycle you spend 3x24 hours sitting in the shade or river doing nothing trying not to overheat during the peak temperatures, and another 4x24 hours huddled in a cabin by bonfire trying not to freeze.

This will make growing anything harder, and since most of the world economy was agrarian at the time will also make everyone poorer. It will also make supplying an army harder, every solder needs 2-3 sets of clothing 1 for cold 1 for heat, or you have to accept that 2 your army can't fight much of the time.

Sleep cycles Humans normally rise with the sun and sleep with the night. In ancient times this was especially true because lighting was poorer quality (dimmer or flickering) than light today and relative to the average person's wealth very expensive.
Even with heavy use of stimulants and sedatives it is difficult and unhealthy for humans to stay awake 7x24 hours and then sleep 7x24 hours. We would have to accept that humans sleep some during the day and work some during the night, increasing the cost of doing anything since you need to pay for light at night. This will be difficult for a society with limit access to time keepers and no alarm clocks or electric light. There are also phycological issues with waking and sleeping out of sync with the sun