Warfare is not something that is traditionally engaged in in any sort of large scale on the island. Most combat involves only a few individuals and is just a swarm of bullets and arrows without rhyme or reason. Knowing how to effectively engage in large scale combat operations can make your tribe unstoppable and can assure that your iron fist rules over a vast domain.

Since Combat in ark can be so varied, and the Island itself is rather large and similarly varied, I cannot tell you exactly how to win any particular battle, I can only give you tips that you must apply to your own situation, apologies if any part of this seems vague due to that.

Also, as a foreword, This might suck, I'm just an engineer who fancies himself a military strategist, I'm not a writer.

It's always stated, but never is the full importance of this statement understood. Intelligence is more valuable than soldiers in combat.

By observing your enemy you might be able to identify the resources they are abundant in, and the resources where they are lacking, and by learning this you can exert an indescribable amount of control over them in their tactical and operational decision making.

Examples are as such

• If your enemies use shields, you can know that they have a resistance to frontal damage, in response to this, you can employ explosives or gas cloud tranquilizers, or encircle the enemy
  
• If your enemy doesn't have any/many flying mounts, you can be pretty sure that they have terrible aim. Keep at a distance to exploit this. The other possibility is that they have only a few narcotics, in this circumstance you can ditch any gas masks, stimulants, or other anti-narcotic measures you've taken and free up the inventory weight and hotbar space for other items.
  
• In any other circumstance, look at the circumstances your enemy finds themselves, consider the consequences, and think of the possibilities. Doing so will allow you to capitalize on their failings, as well as counter their attempts to remedy their situation.

also, behavioral analysis should be considered.
Does your enemy examine their surroundings fully? If not, use traps, ambushes, etc.
Do they favor a certain weapon or dinosaur? Use weapons, strategies, and dinosaurs to counter their fetish choice.
Is your enemy primary land, air, or sea based? set up traps or defenses to effectively act against that strategy.
Does your enemy have turrets, exposed electrical or irrigation systems, utility dinos such as dung beetles or Gigantopithecus? Destroy those to strain their supplies and make their defenses less effective.

Everybody's favorite, and also the stupidest thing you can do.

I get it, open battle is cool, glorious, and the simplest to think about, but it's not actually that important, nor is it strategically advantageous. Avoid it where possible, but in the event it must occur, have a plan.

If you are a numerically inferior force, run. You will get your fudge packed
If you are a numerically superior force, encircle the enemy to prevent their escape, whether with melee weapons or with ranged, surrounding the enemy is a wonderful thing. Attacking from four sides is a whole lot better than just one.

Have a robust organizational structure in place (group men into some type of unit, if you're lucky you might get three contubernia). In an open battle you need to be able to control the battlefield with nothing more than your men.

Of course, this isn't the days of old, where battles were fought by legions of men with sword and shield, so even a larger force can take heavy losses. An Argentavis carrying a man with an assault rifle or bazooka can inflict huge damage.

This is the area where I'm least knowledgable, so if any commenters want to give advice, feel free to.

If you can steer the enemy into the right location, you can win any battle you want.
Smuggler's pass, the Hidden lake, the Western Approach, the southeast shores all hold good positions for ambushes. Any cliff, bluff, beach, River, Valley, etc is a potential victory. Perch artillery atop any hill and a mounted unit is unable to respond, anything other than another artillery unit is useless. even so, the unequal footing gives you an edge.

At the same time, these locations can be some of the most defensible, and provide other opportunities. Small obstacles such as wooden walls and metal spike walls with, for example, a Paraceratherium with a mounted autoturret can stop an convoy dead in it's tracks and do massive damage while also providing a quick getaway if the worst happens. Get behind the enemy with trikes and you can push the enemy into the metal spikes, the enemy, even if they're larger in number and with superior dinos, being attacked on two fronts can't do much here.

Swimming and beaching are difficult in ark, and many rivers are too wide for light artillery to fire across, this makes any beachhead easily defensible by even a small contingent of infantry or cavalry.

If your enemy uses large dinosaurs (Trex, Spinosaurs, Diplodocus, etc) trees are useful, especially in the Southern Jungle. You can hide your troops under the low canopy and do significant damage while your enemy struggles to even locate you.

To have control of the redwood forests is to have a position that is virtually unassailable. Since the large redwood trees cannot be chopped down, platforms built there can be built out of range of land dinos and can rain hell upon your foes with almost nonexistent risk to your structures or any troops, items, or dinos held therein.

Really, Don't

• Don't
  
• Don't
  
• Don't

Don't

To elaborate, IRL Seiges took a long time
Anywhere from a few months to 21 years.

Their main goal was to isolate the city from it's food source, from other cities, and to lower morale among the enemy. Since farming is usually done within a base in ark, and there's a global chat, 2/3 of the goals of a siege are impossible in ark. That being said, you can lower morale. basically construct your own base around their base and wait until everybody has fled.

Sieges are really impractical because you need to keep constant watch and you need roughly 5-8 X the number of men in the base in order to effectively siege it, and the zone around which you cannot build means you practically need another base' worth of materials to siege.

If you must siege, it won't be in the traditional sense, It'll be more like raids. just get some argentavis in to drop large numbers of defensive herbivores into their base (Carbonemys, Trikes, Doeds, Ankylos, etc) if they try to attack these they'll be overrun from within and some structure damage will be done. Equip some men with RPGs and take them up with Argents/Pteranodons to take out vital base elements (Turrets, Refrigerators, Farms/Irrigation, generators, Plant X, Dung Beetles, or just anything out in the open)
the ultimate goal here is not to starve them, but to break as much stuff as possible to make an actual storming of the keep more possible, or to force them to use resources to repair damage instead of using resources to kill you. Eventually they'll run out of one resource or another.

Anything you can use to influence a battle is worth doing.

Setting up Narcotic traps, setting up ambush rooms (a 3x4 room with a 1x4 pathway flanked on either side by 1x4 rows of hatchframes, with each holding a soldier armed with a narcotic crossbow), IEDs, C4, distractions, bear traps, literally whatever you can think of.

this includes environmental threats. The Swamps suck to cross, so if your enemy has to cross the swamp, it's likely that something or somebody is going to either die or contract a disease while in it, and that will screw them. If you can somehow force your enemy through the tundra, do that. Any condition you can inflict upon them that you can either avoid or counteract gives you an edge.
Dilophosaurus is really annoying because they nearly blind you, employing a lot of these can make your fight a lot easier

EDIT: I thought this would be the place to include Bolas and shields
Immobilizing an enemy is extremely useful, as it prevents routing and permits you to get up close and personal to artillery units like dilos, thorny dragons, or just any sod with a gun or bow. Use them whenever you're bigger and tougher but slower than your enemy, or when you're being pestered by ranged attacks. (Conversely, try to avoid being Bola'd if you find yourself in the opposite situation.
Shields (and armor) allow infantry units to soak up way more damage than they should be able to, Bieber they are ineffective against narcotics and explosives, and a high-knockback Dino can easily break up a shield wall, therefore they're best utilized against velociraptors and other similar dinos (and they allow an infantry division to take down units that would normally tear them apart by encircling them while the unit tries to take down the shields)

Generally, My opinion is that if you can't win with only your men, units, and strategy, then you shouldn't be fighting.

I will concede this stance on one area though, stimmies and dimmies.

The potential of Narcotics is never fully appreciated, it's a quick way to take enemy combatants out of the fight until the biggest threats are dealt with. You can later just mop up after and kill them while they're defenseless. If narcotics are so important, stimulants are just as vital, for their usage directly counteracts narcotics, which allows your units some defense from tranq arrows, narcotic traps, poison grenades, tranq darts, electric batons, clubs, scorpions, pachys, and just plain old battle fatigue.

Even if you can't knock out enemy dinosaurs, immobilizing their riders prevents them from organizing and limits their capability to attack, which might turn the tide of a battle.

A robust defense is important to maintain. Defense can be categorized into two main types of defense: defenses intended to prevent base entry, and defenses intended to correct base entry.
Walls and ceilings, any form of barriers are the most obvious way of preventing people from entering your base, intending to physically stop entry, but these systems can be overcome through time, dinosaurs, explosives, etc. Thus it is good to have multiple layers of defense, both passive and active.
Passive defenses are turrets, plant X/Y, traps etc. Active defenses are anything intended not to keep enemies away itself, but to make defense easier for Players.

Dinosaurs can also be used for defense, merely setting them to aggressive in their pen makes entering that pen a difficult prospect.

Defense can be made easier by selecting a strategic position, whether it be a location inaccessible to gigantosaurus and titanosaurus, or protected from most attackers by a freezing cold climate and megalodon filled waters, or atop a mountain with only one viable land route to reach it, the terrain can greatly influence the defensibility of your base.

Turrets are of course a go to method of defense and that is for a reason, their versatility and effectiveness can not be denied.

Another thing to consider is types of units and their location relative to other units, as well as whether they are manned or unmanned (or partially manned) as well as the purpose of your outing.
If you're foraging, there's no reason to bring more than the Dino you're riding, a Dino to carry collected items, and a defense Dino. If you're raiding, you're going to want significantly more than that.

If you're expecting to run into hostile players, consider the benefits and drawbacks of having certain dinos as Frontline troops. Arthropleura quickly tear away at armor but are slow and block dinos behind them from giving chase if your enemy routes. Dilos impact the vision of enemies and slow them down, but can't be ridden so you must either be attacked first or whistle 'attack this target' with perfect aim in order for them to engage. Ankylos do respectable damage and have a knock back that keeps melee enemies at bay,but this may price detrimental with targets that prefer ranged attacks, as they are slow and block dinos behind them.

Other dinos like raptors gave no way to immediately respond to ranged attacks and have little health, but do great damage, have high speed and maneuverability, and are small enough to let dinos behind pass without much struggle.

Of course, you should also consider which dinos you don't want as Frontline troops. Such as morellatops. While their meager damage can take out infantry, against even small carnivores they show how vulnerable they are, and losing them means losing easy access to water,which makes expeditions and raiding much harder to sustain.

Again, you want to consider (especially if you have an unusually large flock) what you do and don't want as rear most guard, ad they are vulnerable to being caught on terrain and lost without you noticing and being picked off by either wild carnivores or hostile tribe members before you can properly respond.

Really, exactly how you should organize your dinos is up to you and dependent on your circumstances, but you should be able to recognize when and where certain dinos should be put in certain positions.

Thanks to reader comments for suggesting editations to the guide, and to the tribes I've been a member of for allowing me to experiment with the dinos they've worked so hard to tame.