During the early 1800s, various countries are gifted tall and modern ATVs (All-Terrain Vehicles). These ATVs require no fuel and come with manuals. After a few months of trials, many Europeans master the automobile. They decide to use it in warfare.
Could the ATV effectively replace the horse in 19th Century Warfare? Specifically when it comes to direct combat?
By the 19th century, cavalry is far from obsolete; multiple new types are becoming popularized by evolving conditions in warfare. Let's take a survey of the horse and where an ATV would actually help:
Shock troops whose role was to panic and rout the enemy would benefit greatly from an ATV, which makes a loud noise. However, the ATV lacks two critical advantages of the horse: height and handling. A lancer 6ft up on a charger is a lot more physically intimidating (and safe from attack by bayonet) compared to a waist-level opponent.
But more importantly, after the cavalry delivers their charge, they need to reform, turn around, and charge again. A horse, once stopped, can do this on the spot. An ATV would require a 2 point turn or a pivot of the entire formation, which required considerable training to pull off.
The high speed of an ATV makes it very good for one function of light cavalry: pursuing fleeing troops to cut them down. As losses of an army were primarily generated during this phase rather than the combat, this would make ATV light cavalry extremely potent.
Their speed also makes them excellent for carrying orders during battle (remember, this is not Total War, a general can't just select a unit and order them where to go) and as screens for an army on the march.
However, it would not be very good for the other combat purpose which light cavalry served: skirmishing. The noise of a gasoline engine more than compensates for the lower profile. The best use of ATV cavalry in this case would be to spring an ambush, fire a volley, then get on their ATVs and run away.
The Napoleonic war is when we see a new type of cavalry emerge. Well, not quite cavalry, but mounted infantry: soldiers who would ride to their spot on the battlefield, then dismount and fight on foot. Needless to say, the value of these ATVs would make intentionally abandoning them a ridiculous prospect, and enemy armies would prioritize overrunning these units to pilfer their priceless ATVs.
They would not risk these amazing motors.
It is 1820. We have been using coal fired steam engines for our motors. They are huge, heavy, dirty and they explode. And now we have a powerful electric motor that needs no fuel? And we are going to put this miracle in the care of a teenager with a sword and let him go charging around getting shot at with cannons? No, no no. These motors are priceless.
The teenager can ride a horse. The fuelless motor from that ATV is going to run a shop of machine tools and take the place of a coal fired steam engine. This other motor is going to power the motorboat of the princess, who does not like a sail occluding her view and does not like the smell of smoke. Each of these motors is spoken for either by very rich people who want to show off in their amazing vehicles, or very rich people who will use the motors to become very richer.
The ATV would certainly replace the horse, but not for cavalry.
One thing most people don't realize is just how much effort goes into moving supplies for an army. Prior to the invention of the railroad, anything that moves food, also eats food. An army's operational range caps out at only a few hundred kilometers from its supply base, at which point the roads are clogged with supply wagons mostly engaged in the business of carrying food for their horses.
Your ATVs change this balance dramatically. Instead of each freight wagon needing to carry food for a driver and two horses, a single driver on an ATV can pull a string of wagons. This reduces the food requirement of your logistics train by at least a factor of ten, with a corresponding increase in operational range.
You might have scouts or messengers on ATVs (the extra speed is a nice boost), but mostly they'll be seen pulling wagons.
No
Your body is an absolutely amazing thing. Without any conscious thought, it will self-correct to maintain balance while walking, skipping, even (and especially) running. Your body has the ability to deftly dodge obstacles large and small. It's ability to reshape itself, thereby shifting around its center of gravity, is one aspect of this these amazing abilities. Your inner ear's operation as a biological gyroscope is very much another aspect of these abilities. Your body also has the ability to side step, to place your feet where they need to be to change your acceleration and direction of travel. They allow you to pivot in the process of shifting your weight and direction or speed of travel.
Horses, of course, can do this, too. I recently attended the Montana State O-Mok-See, which is a series of pattern horse races. It's breathtaking what a horse can do at high speed.
ATVs are nothing at all like that. Yes, the rider has an itty-bitty bit of ability to shift around the center of gravity, but that's it. ATVs can't pivot like a horse, or shift its weight like a horse, or keep itself upright like a horse. Shooting a gun from atop an animal that can (with training) control itself while the rider lets go of the reins and keep a predictably smooth gait over uneven terrain is easy compared to keeping one hand on the proverbial wheel of an ATV and noticing that its suspension is nothing at all like the gait of a horse.
In fact, people who try to use ATVs like horses are hurt and injured every year.
And horses can go places ATVs can't.
So, why do most modern militaries not ride animals? Because animals are expensive. They have costs to feed and keep healthy that mechanization don't. You can empty the gas tank, deflate an ATV's tires, put it on blocks, and throw a tarp over it for years and it'll work just fine. Can't do that with a horse.
But it would be worth your time to read through that last link, because there are modern militaries that do ride animals into battle — and they have good reasons for doing it.
But it's worth pointing something out
Guns.
Perhaps the biggest reason horses left the modern military is that guns developed to the point where the horses became irrelevant. Horse vs. machine gun and the machine gun will almost always win. If in your scenario you do NOT have significant guns (early 1800s, probably not) then the horse is still a very valuable asset that an ATV will be hard pressed to replace.
But once those guns come into play, horses quickly become a liability save for a handful of special-purpose scenarios.
I believe Willk is on the right track, but I think some of the motors would be risked in combat. The engines could be used as auxiliary engine for formerly sailing ships of war, allowing them to maneuver against the wind, or in a calm. The advantages are impossible to overlook, and worth the risk to a few engines.
There's a lot of good reasoning in the existing 4 other answers, but they all miss something, even if they graze it.
Yes, these ATV's are highly valued as motors, but that makes them great for bait in an ambush.
At first, I can see many of these machines being used for combat and anything else that can be done with them, foolish or not. I mean, just look at how people use them now.
But as they become more rare and as people realize just how many things they can do, and then come up with really valuable ways to use them, they will be used less and less for combat, for the most part. There will still be some Generals that are so vain they "require" the use of the Royal ATV as their steed, or whatever. And there will be people and countries that will go looking to acquire/steal them at any cost, even if it's to hoard them and prevent anyone else from having them.
So some of the best armies will have these machines, regardless the risk. And the smart armies will use them to bait enemy into traps. The best way to catch a thief is to catch them in the act and the best way to do that is to make it a controlled environment for the captors. This works on a group as well as an individual.
A larger army may not be as easy to get into a trap as a burglar, but that's why you use the size and difficulty of a trap and bait to match the quarry. One ATV might not catch the eye of a General, but it could a Corporal. Five ATVs might engage a Major. More than that, plus you make it hard on the army to catch the ATVs so they stop looking for traps after the first couple miles/kilometers, and you might just bag a Company and some higher ranking officers. Even if those officers aren't in the trap, they could now be fairly insufficiently guarded so they could be rounded up later or a secondary group of soldiers could capture them while the chase is still in progress.
Could they still be used on combat? Sure, but that's a high risk and low reward situation that can be altered by simply using more people so it becomes less risk (the to Crown) and higher reward in that you are overrunning the enemy by just pure mass of people, which was the tactic of many armies even after guns were introduced. (Look at WWI, for instance.)
There may be limited use with specialty troops that harass any army into engaging before they are ready, or that quickly flank rearward artillery or other long range weapons, but that would be a relatively small group and the reward would have to be extremely high to merit the high risk of losing these valuable machines. Likely, these troops would be using the ATVs that normally tow the larger war machines, like cannon and Gatling guns.
Could they be used in the supply chain? Sure, but the supply chain itself is a high order target for an army. It has fewer soldiers and can serve to supply an enemy army. Adding high value ATV's as the motive power for these supplies will increase your need to have a large force guarding it to the point where your army might as well just surround the supply chain. Unfortunately, this doesn't really get you very far when your army has to continually to return to base to guard the next shipment of supplies to itself.
No.
A good horse can be controlled with legs alone, leaving two hands to handle weapons. An ATV doesn't have leg controls, nor does it respond to voice.
If you want a small mechanized combat vehicle to put in your time machine, look at the jeep+machine gun combination. Assuming you could keep them running, and could provide ammunition, they would be close to unstopable in reasonable terrain. Mind you, the driver would need good situational awareness. Enough cavalry could ring them in with dead horses.
H.G.Wells considered this in The Land Ironclads. This was published in 1903, so he just didn't make it into the 1800's but it is a useful idea of how people might think. This was not just tanks: he had their light cavalry equivalent on motorbikes.
I wonder whether the army would have trusted the ranks with complex technology in the early 1800s. They were considered cheap, and expendable. The Navy already had trained men working with a complex machine. There were people who considered sailing was somehow 'pure', but there were others who saw the possibilities of running into the wind with an engine. Powered ships were in use in the US in the mid-century. This is not like cavalry, as navies had no real equivalent to that.
