How to alert Houston of the coming barbarian invaders in time, without instant communication?

Question

Background

Centuries ago, nuclear inferno engulfed the world, and billions were killed. Most people were knocked back to Texas, one of the mightier states in the bygone era, was split up into many warring city states. Texans near the borderlands were absorbed by Mexico, while others were annexed by the main Texas cities, which are Laredo, San Antonio, Austin, and the two top dogs, Dallas and Houston.

26th Century

Texas ha started to hit extremely turbulent times. The two main cities from before have annexed many of their neighbors. Dallas is by far the biggest empire in Texas, and have a territory that stretches from Chihuahua to Oklahoma, and they’re getting rich from it. But not as rich as Houston. Houstonians have access to the Great Gulf on the east, and the San Antonio River. Taxing all the merchants who come from across the Great Gulf has given them a great income, and Dallas is jealous. Dallas has lost a lot from the failed invasion of Klaho(Oklahoma City) and people are starting to question their king. King Lorvert IV Of Dallas has a plan to take over Houston, and he has to get the help of a few thousand barbarians to do it.

Lubbock

Lubbock has become a wild wasteland, with many tribal clans fighting and warring with each other. The only major power in that region is Yellow(Amarillo) and it is forgotten about by most Texans. The Lubbock tribes are primitive, fighting with spears clubs and arrows, but King Lorvert has an ingenious plan. He has forced the Gun Runners, a company of weapons-manufacturers up to Lubbock to strike a deal with the Lubbockians. They send up Guns, Cannons, and Horses to the most powerful of the tribes, in a show of fake friendship. One day, a messenger from Dallas comes to Lubbock, and tells the tribes that Houston is currently invading Dallas territory, and that they must invade Houston to stop it. But, in reality, Houston has not invaded Dallas at all, and no Houstonians know what’s about to hit them.

Battle of San Antonio

The Lubbock tribes, armed with the guns and cannons and horses, and led by a detachment of Dallas soldiers, march through Dallas territory, and finally they reach San Antonio. The city of 50,000 is sleeping, as the tribes reach the iffy at early dawn. But, a few soldiers on watch at the time notice the tribes and soldiers, and alert everyone else. The entire military of San Antonio is scrambling to shot down the invaders, prepare cannons, and get ships going down the river, but it’s no use. The force of 10,000 men easily take down the smaller, less experienced garrison at San Antonio. They get past the city walls, and start hacking people to pieces and capturing them for enslavement. The also kill every single horse and messenger, so it will be impossible to warn Houston about the invaders by messenger. But they must warn Houston.

My question is some other way, besides by messengers, that San Antonio could warn Houston about the coming invaders? Something based on actual past history would be really nice, as I prefer my Worldbuilding to have groundings in reality.

Map

-Everything in Black is Houston Territory

-White is Dallas Territory

-The red arrows are the path of invasion by the Lubbokians

I based my future history of Texas on medieval and Renaissance Italy, when it was divided into many city-states. Dallas is supposed to represent Florence, while Houston is supposed to represent Venice. Of course, I expanded their territorial space, and added some barbarians just for fun. I put a lot of work into this, and so I’m glad to share it with you all.

Answer 1

I can think of a number of ways any warring state should have available with Renaissance-like technology as you suggest.

1. Homing pigeons: not difficult to re-breed from the feral, ubiquitous, city dwelling descendants of the possibly-lost-by-the-26th-century breeds of old. According to an unsourced Wikipedia statement, [t]heir average flying speed over moderate 640 km (400 miles) distances is around 80 km/h (50 miles per hour), faster than horses. They will remember and be able to travel back to the place they were raised as soon as released. It was part of the defense and diplomacy of Medieval kingdoms to share a few with allies or between cities in the same kingdom.

   

2. Beacons: Remember the siege of Minas Tirith? They are set atop the highest mountains and are agreed specific meanings like: "Help! We're under attack!". Their fire is obvious by night and not too difficult to see in daylight. The message travels at the speed of light, except when a new beacon needs to be lit. Guards keep them functional and watchmen must look at them as part of their job description.

   

   Their range is limited, though. Especially in the area you describe, you'd need a network of beacons atop hills or towers to cover the 200 miles that separate San Antonio and Houston. As a reference, a beacon at 200 meters (660 ft, a little less than the difference in heights between both cities) of altitude, could be visible from 50 km (31 mi) at sea level under good weather conditions, provided there is no visual obstacle (like other mountains). Texans could be interested in building such a network, if the loss of a surprise attack is worth the investment on the network.

   You can do a rough estimate of a beacon's visibility range by assuming the Earth is a sphere and using Pythagoras's theorem (the results won't be perfect, but they won't be too biased either):

   

   $d=\sqrt{6.3712^2-6.371^2}\times 10^6\,m\approx5.048\times10^4\,m=50.48\,km$.

3. You could replace or complement beacons with smoke signals. It's not difficult to make big fire beacons generate a lot of smoke. Columns of hot smoke (in absence of wind) can add a couple of tens of meters height and increase the range of your warning signals. The color of the smoke can be easily engineered through the appropriate fuel to white (green vegetation) or black (oils, less oxygen, tar, paper). Smoke works obviously better in daylight.

4. If the technological level allows it, fire beacons could be replaced by Semaphore lines. Either mechanical arms or color flags would work, but you need either a much more dense network, or telescopes, which are late-Renaissance. They allow for written messages, just as the telegraph or email

5. If everything else doesn't work in your world, there could also be relays of horses or some other animal. They are even faster than cavalry, since relays allow constant sprint speed.

Update:

Regarding a relay of cannons, suggested by G0BLiN, all I have found is that the Ottoman empire cannon's (XV century) could fire heavy stone balls a mile, and the sound of their blast could reportedly be heard from a distance of 10 miles. In order to keep a stable way of emergency communication you'd need to permanently immobilize 20 pieces of artillery to cover the distance between San Antonio and Houston. Unless you have 20 towns you are willing to waste a cannon to defend, woodpiles are cheaper, and towers are less tempting to move somewhere else.

As for heliographs, as suggested by Thucydides, they could be a possibility, depending on how much you are willing to twist history. They were invented in the XIX century, although you could build one with a mirror and good navigation technology from the Renaissance (telescopes, precise mechanical machines) to point it. Morse code is also XIX century, but your peoples could kind of remember the idea from the past or plausibly reinvent a set of codes meaning different messages. Heliographs are better than (fire) beacons in the sense that you can send a variety of messages, they have the same reach and restrictions as beacons, but are useful for sunny days only—unless you have an equivalently powerful source of light (or an extremely precise parabolic mirror not available at the time).

All factors considered, I think homing pigeons are by far the best option. They are very reliable—one of them even carried a message wounded during WWI—, they fly—so they could be dispatched in time and easily dodge messenger-killing attackers while other watchmen warn everybody else, and could reach Houston in 4 hours, while the attacking cavalry couldn't get there in less than 2 days (maybe 3) and the heavy artillery/infantry in more than a week (3 mi/h, avg. 10 h a day of walking... with cannons).

Answer 2

Lots of people come to big cities at dawn. I am thinking farmers who come early from the countryside to set up their wares.

These folks would be coming in from all directions as the sun rose and they would see the battle, possibly from some distance. The attackers could take out all inhabitants of a walled city but not the entire surrounding area.

Some of these early risers might get closer to see what was going on. Some might go home. Some who realized what was going on might head for the nearest big city. They might have varying stories depending on how much they saw and what sort of context they would put it in.

It would be hard to so completely exterminate an entire region that no word of it would get out.

Answer 3

Cannons are loud.

With the right weather conditions, it's plausible people outside the 'kill zone' could hear the battle. A low-lying and flat cloud-cover would help keep the sound from dissipating upwards. Also humidity seems to help sound travel farther. The sound would travel especially far through valleys that stretch outwards from the source. Valleys or mountains perpendicular to the source would absorb the sound. Dense forest would absorb the sound.

At first glance the geography of the area makes this seem possible, but you've studied it more than I. For distance estimates check out this thread on people hearing civil war battles: https://groups.google.com/forum/#!topic/sci.military/6zjZBvtJl8I

Some accounts claim battles were heard as much as 150 miles away which from San Antonio is already most of the distance to Houston.

Answer 4

Other people have already provided workable solutions, e.g. beacons or birds. I'd only add sound based signals, e.g. dry firing a cannon or using explosives at a hilltop in a chain all the way to the city.

However, those might not actually be required since a normal person will most likely arrive far before an army could, even on foot. That is, unless every attacker had horses, the cannons were lightweight and the attackers expected to find food everywhere they slept.

A roman army could probably march around 30-50km a day and they were trained for endurance long before they started to receive combat training. They also had the advantage of roman roads. I can't find good numbers for armies of the american civil war, though google results suggest a speed of 15-30km a day. Unless your warbands have military endurance training, it'll probably be around 20-25km a day. The reason for that is not just the endurance, which mostly reduces the expected top speed, but also the required logistics behind it.

As a rough guess, an army of 10'000 men doing hard work requires around 20 tons of food and 40 tons of water each day. Your horses might also require food and water, depending on how many there are. A small batch of horses can feed on grass in the wild, though whether you find grass in a place that 10'000 men walked over is never a sure thing. You'll probably need food for the horses. A horse eats between 1.5 and 3% of it's body mass in food each day, let's say 10kg food and 10kg water a day. Estimating that 10% of your army consists of riders, that makes for another 10 tons of food and 10 tons of water. Where is your army getting 30 tons of food a day from? A cow produces ~250kg meat, so your soldiers would eat 80 cows a day. Unless your army happens to stumble upon farm after farm rich in cows, you'd have to bring the food with you. However, soldiers can't carry unlimited amounts of food in addition to their combat gear, and your horses need to be supplied as well anyways.

In summary, you need a logistics train and carts. Carts mean you either need roads or you need to prepare a way for them to move behind the army, i.e. remove trees, roll away rocks and such. If you have roads, great, your carts can move about as fast as a human can walk, around 5km/h. However, roads rarely go in a straight line towards where you want to move. You also have to consider that 10'000 men just walked over the road your carts are using, so it might no longer be recognizable as a road unless it was fortified, which means carts get stuck and stop all other carts behind them from moving ahead. If you don't have roads, well, expect your daily speed to go down a lot. The requirement to supply a large army is a big reason why the famous fortified roman roads were built behind the advance of roman legions.

In addition, your army would probably want to prepare a camp each night, i.e. digging out latrines, preparing some minor fortifications and such, just in case the enemy did know they were coming. That limits the amount of time the army can spend marching. Lastly, you want your army to arrive without being exhausted, so you'll probably need an extra night unless your last rest was just 10km away from your target.

Your army is bound by the requirements of logistics, which a single wanderer or a group of them isn't. A lone person can easily forage and move in a straight line, but an army can't. Imagine telling 10'000 people that marched all day that they have to go to bed without food, because you couldn't find a farm to plunder today. You'd probably wake up with half an army the next day.

It would just take a single hunter or forager spotting you from afar without you noticing, who then proceeds to move at his fastest walking speed cross country to your target to warn them in plenty of time for them to prepare. Since you are in hostile territory, the probability for that happening is extremely high, a 10'000 strong army isn't exactly covert.

Even if you do a forced double speed march, for which your soldiers will hate you, you'll need around 6 days to cross 300km and your army will arrive tired, exhausted and probably very hungry. A lone hunter can cross that distance in 4-5 days on foot, giving your target at least a day to prepare. At a normal marching speed and adding a night rest before the battle you'd need two weeks for that distance, which gives your target more than a week to prepare.

Answer 5

First stage: San Antonio to somewhere nearby

It is very likely that somewhere near San Antonio there are horses or other means of transportation. While all "official" messengers may have been killed, someone might have hidden himself - or played dead - and could reach beyond the battle area. If they kept their wits, they should be able to dodge patrols sent to intercept messengers.

(Alternative)

If somebody heard the battle from far enough, and believes the information to be worth something in San Antonio (it's unlikely that the warfare situation would be a complete surprise for anyone: complete information control is beyond the ken and capabilities of Renaissance-level tribes), or suspected that silencing patrols might attempt to remove uncomfortable witnesses, they might decide to run for it without ever coming near the city.

Second stage: from somewhere nearby to Houston

The Lubbock tribes will require a substantial time to regroup, secure their loot (and slaves), and prepare to proceed towards Houston, even having coming prepared.

In a pinch, you might need to reincarnate an Apache Spirit Runner to make the San Antonio - Houston tract in under four days on foot. But otherwise, the Lubbock army isn't likely to do more than fifteen to twenty miles per day, nor leave inside a week. So it will be at least fifteen to twenty days before Houston is hit. A pilgrim-paced individual (e.g. those making the Camino de Santiago) can do that in half the time. During the Renaissance, pilgrims routinely walked more than that.

Answer 6

Even in the days of horse-drawn cannon, you don't generally hear about sneak attacks taking entire city-states by surprise - particularly if tensions were high between the two regions, as you've suggested.

Houstonian spies would presumably have been keeping an eye both on Dallas and their new friends to the north, and any armed force advancing through Dallas' territory towards Houston would not go unnoticed. It might be that in the spies' urgency to get the message to Houston, they feel that San Antonio can be sacrificed, but there's no chance that ten thousand armed men plus supports could invade Houston's area without Houston knowing they were coming.

Answer 7

You don't need "dedicated" messengers, you just need a few nosy people that have seen the battle from a distance.

As has been pointed out by SCMorfildur, armies are SLOW and limited by supply. A single person is not.

I think this is something that needs a reframe--the question isn't how the news would get to Houston given the army in San Antonio, it's how it wouldn't get there.

You're looking at the impossible odds, I'm looking at the fact that it just takes ONE person getting away, seeing (or even hearing) the carnage or even the army itself, from a distance.

It's an army of 10,000, and they have to cross some elevated terrain to get to San Antonio. There are bound to be people who live there who know the territory and who will hide as they pass. They will not get all of them. It's those folks that will warn Houston--they might even gather intelligence as the army passes, knowing that it's too late for San Antonio, they might just head straight for Houston, or follow the army, watch from a distance and head to Houson.

But I take umbrage with the fact that San Antonio would be totally unwarned--an army of 10,000 is not sneaky or stealthy. You can have scouts but they might not cover everything (it's inevitable that they won't).

Some questions:

1.Do your barbarians set fire to anything? When a city is sacked, some of it tends to burn, especially when cannon and gunpowder is involved? That right there will tell people for MILES that something is up.

2. The whole enslavement and looting thing--how long is that going to take? I'd estimate that your barbarians will spend SEVERAL days looting the city and enjoying the riches. They came a long way, and this sort of thing is important for morale and health (they need to stock up on supplies and eat well while they can). You're asking "how ever will Houston know in time?" I'm saying that even without the logistics of a supply chain and moving an army, they WILL LOSE several days here.

It feels like you're using this as your model: The Battle of Carthage Even though you said Renaissance. Roman cities were a lot more populated then than they were later. The Roman army is far more organized than a barbarian horde might be--but this might depend on the given definition of barbarian...

You have other problems--disunity. In your background, you said that the tribes fight each other. And here you have an army of 10,000. I presume there is loot, they are armed and they still don't like each other. This may also buy time...

A smart barbarian leader would be questioning the populace about the supposed invasion of Dallas by Houston. And he'd know the difference between stuff said to avoid torture and the truth. Barbarian doesn't mean stupid. It can mean savvy--and if San Antonio is as ill-prepared as you say, they will notice, and they might ask themselves WHY. They might also ask why there weren't scouts through out the countryside as soon as they hit Houston-ruled territory. It's definitely what the barbarians would do. The questions leadership might have, and the finding of those answers-- may also buy time.

You keep hammering away at "how would they get the news in time?" I'm saying that there are a number of complications given your background, plus the logistics of moving an army that would give an individual, even one on foot more than enough time to get the news to Houston.

On a practical level besides nosy people/unofficial news carriers, the answers of signal towers, homing pigeons and cannon fire are good ones from Rafael.

If the folks of Houston are smart, they will have people in the country side charged with getting news to them--the battle itself--with the cannon fire, not even a signal one, just one being used in battle, is enough to even get folks who haven't even SEEN anything to report back that information.

Answer 8

Homing pigeons are a great idea. I own a pigeon control company in Phoenix and can tell you from personal experience that even the feral pigeons that we deal with every day are tough birds that can find their way home from a great distance away. They hold up well to just about any weather and are actually pretty smart. I think they would be a great resource.