Short answer - orcs should become more organized than humans, and abuse feudal rivalry properly to capture human lands, while reducing peasant human causalities to minimum, to firstly force peasants work for them, and later, make peasants willingly work for Orcs for fair payment. Anyway, i have Christmas vacation, so i decided to write a long answer. I assume orcs are traditional - strong, muscular and bulky green humanoids, but, "they aren't less intelligent but more aggressive (than humans). They have less advanced technology but it's caused by lack of education and mostly nomadic lifestyle in past", and they have Shamans with some mystical powers.
Short excerpts from "Why Orc strong and Human weak" - book written by Orcs Shamans, printed on fine sheepskin (and, sometimes, on skin taken from executed human outlaws, exiled orcs and corrupted officials) and distributed among all Orcs settlements by order of WarBoss-of-WarBosses Doldon the 47th(let the GodMother warms his footprints).
This book is translated to Humans language, and every infant (both human and orc) should read this book. And every Warboss and Humans' governor should have this picture of Great Doldon the First WarBoss-of-WarBosses at his or her chambers:
Orcs are strong, because we have pretty ladies. Humans don't
Just take a look at this sexy pointy ears of this hot babies.
Even if you cannot distinguish, which ones of this 4 orcs are males, and which one is females, its ok. Humans has issues distinguishing orcs.
But our ladies like to born children more, than human ladies do. And its easier for them, since infant orcs are smaller than human infants, usually there is 4-5 ones per single birth. So, if there is plenty of food, orcs breed faster than humans. And humans even kill their ladies if they think they cheat with other humans. We don't understand it. Lady is not slave, she belongs to herself only. Also orc ladies loves to fight alongside their man, while humans thinks ladies should never touch weapons, and strong human ladies are not physically attractive. Also we do not burn ladies, if we suspect them in witchery.
Orcs are strong, because we have strong stomach, humans don't. Its honour to donate your flesh to feed your tribe after you die, its honour to eat fallen enemy, both for yourself, because it shows you are strong, and to your enemy, because they did not rot in soil feeding unworthy pests. And, humans are too whimsical and capricious in choosing what to eat. Humans can even catch tummy worms from eating raw meat. Orcs cannot.
Orcs are strong, because we have good Shamans. Humans are weak, because they have corrupted clergy Shamans picks strongest and smartest orcs, and makes them War-bosses. This War-bosses usually pick fights with weaker tribes of other orcs. Long time ago, we had bad Shamans, they cannot listen to Songs of GodMother properly, and orc tribes battles usually resulted in many orcs killed. Humans easily exiled us to mountains and arid plains with little food. We were on edge of extinction, but miracle happened. GodMother fixed our Shamans to understand Her songs properly, also Shamans learned to scream silently to each other, so they can talk, even if they are separated by great distance. Humans call it telepathy. Humans like to invent fancy words to explain things they do not understand. We don't. Now, if 2 tribes want to fight, their Shamans has council first. Than Shamans takes one random orc from every 10 ones of each tribe, or even one of 100 if tribes are big (because GodMother controls, who is lucky, and who is not), and then this decimated warbands fight under leads of their Warbosses. Sometimes there are fights between 2 Warbosses only or two Warbosses and their children, while their tribesman only make bets.
They fight, until any warboss is killed. Than struggle stops, and survived Warboss becomes leader of two tribes. Two tribes joined in new one. So, instead of Dark Bears and Bloody Wolfes tribes, there is new tribe - Bloody Bears. With one Warboss. All orcs had to deny their past and join in new tribe. In worst case, each tribe has every 10th orc lost. So, current tribe struggle is nothing compared to old times when we had bad Shamans - because old vendetas lasted for centuries until last orc died. And current struggles makes tribes united with few orcs lost.
Good Shamans educated us to be merciful, to spare lives of our enemies.
And humans are weak, because they have corrupted clergy. Clergy says good things, but secretly does the opposite. Clergy cannot silently scream to each other. Clergymen cannot listen to songs of GodMother. They make feasts when peasants starve. They make orgies while requiring to celibate. They lie. They serve Knights and Barons by pacifying peasants and motivating them to work in promise for good afterlive in the Land of Dead (while very few of clergyman believes in it).
Orcs are strong, because Shamans listens to Songs of GodMother to find WarBoss-of-WarBosses among other orcs. Humans are weak, because they listen to themselves. GodMother sends Her most bellowed sons and daughters to make tribes work together and make things they cannot do on their own.
Every WarBoss should consider it a honour to serve WarBoss-of-WarBosses. Even if WarBoss-of-WarBosses was not the strongest and smartest one, even if Warboss-of-WarBosses do not believe in his/her path, but it is GodMother who chosen him or her. And Shamans educate Warboss-of-WarBosses to move his Path. To fullfill his Fate. To Unite Orcs. Any WarBoss who refused to serve WarBoss-of-WarBosses, was cursed by Shamans and become exile. And even the youngest orc knows exiles are considered feast food for celebrations! If WarBoss-of-WarBosses is killed or dies, its not an issue, because GodMother is wise. She already send few backup WarBoss-of-WarBosses Shamans are aware off, and Shamans can easily promote any backup one to next WarBoss-of-WarBosses. WarBoss-of-WarBosses makes WarBosses fight together, WarBosses make orcs fight together. WarBoss-of-WarBosses brings order among orcs.
For humans - its nearly impossible for King to control other humans. They say - "My vassal's vassals are not my vassals". Humans fight each other too much. And if King dies, there is dramatic rivalry among his children to choose who will be the next King. So, Humans cannot make big things like Orcs can do. Humans are selfish. Orcs are not.
Orcs are strong, because they show Mercy. Humans do not Even pre teen orc girl can kill adult Human with bare hands. But is it worth it? Human is tasty, you can make brief dinner for few orcs from him. But, if you butcher cow, you can make feast for much more orcs. Cows meat is beafy. Tastier one. And cow is easier to breed, and even human slaves can do it for you. So, why not eat cows and make humans do the work?
If you make human slave, he/she can make things for you - grind your axe, grow crops (yes, they taste terrible, but they are edible), catch fish for you, make your armour and shield, build roads, wagons, ships etc... Human slave can make all boring things Orc considers unworthy. Human has little nimble fingers, Orc do not. But Orcs can make human work for them, and humans - cannot do Orcs works for them. Orcs can convince (without unnecessary violence), Humands cannot. But human slaves are lazy - they don't like to work, and they are cunning, they always plan to flee. Humans are bad slaves. But can we make Humans good slaves? Yes, if we can give them some grade of freedom and respect. Totally yes, if we use their weaknesses properly.
And what can we say for humans? If they enslave orcs, they treat them worse than cattle. Barons sometimes treat peasants worse than hunting dogs!
Orcs are strong, because they know great weakness of Humans. Humans are greedy. Orcs - not.
If you kill Baron and plunder his castle for golden coins and other fancy things Humans like (and Orcs not are interested in), you can give this trinkets to
peasants of this Baron in exchange of crops and cattle. Instead of Baron, Orcs are not interested in hoarding shiny little things, so Orcs want less. And after some time, peasants will learn, that Warboss and his Orcs gang are much less trouble than Baron and his knights. Yes, Orcs are noisy and smelly, and Humans are easily offended, but after some time Orcs will only leave Barons castle to punish outlaws, guard trading caravans and collect taxes. On the same time, warband of 100 orcs is easily to sustain than Humans warband of 100 knights. We are not greedy, we don't need decorated armours, golden trinkets and expensive swords and warhorses. And we are not interested in PFclcDb (hard to translate) physically attractive human teenagers like Baron used to do. Orcs warband offers better protection from outlaws, rival Barons and other Orcs tribes. Orcs brings order, order bring peace. All loves peace, order and justice. No matter who brings it - human or orc. When Warboss-of-Warbosses Doldon the 3rd was simple Tax Collector, and human governor tried to trick him, explaining they had famine and they did not have any food and spend all gold on buying supplies, Doldon dealed with it. Everybody was waiting for Doldon to burn castle and village and brutally kill governor, but, instead of it, Doldon showed Mercy. He put governor on leash like dog, and, alongside with villages, pillaged governors castle, forcing governor to show where he hides his stashes of gold and other shiny trinkets. Half of governors belongings was taken as taxes and other distributed among peasants as compensation. After this, governor was forgiven, he was restored in his rights, and, since this time, he and his children became one of best governors. They stopped stealing part of values they should pay as taxes to Warbosses. And, this is how GodMother showed both Orcs and Humans how things should be done.
Orcs are strong, because we are good fighters, and we fight together. Humans are not. They fight for themselves. We fight, because we love it, and we love GodMother, we fight in honour of GodMother. And to make future Orcs proud of us. Humans are weak, because they fight mainly for pride, power and gold. Humans fight for their Ego. For their selves. Good Shamans explained it to us, and this is why we win. We did not destroy human civilization. Humans are peasants, clergymen and knights. We took place of knights, because we are better protectors for peasants. And peasants are not fighters, they happily work for ones, who demand less. Usually we made siege for Barons castle. All peasants usually hide in woods nearly. Its ok, we are not interested in killing them. We are more interested in making Baron surrender, or, at least, killing Baron and plundering his castle. And it is easy.
We, orcs, are good at paying human traitors. We are not greedy. And human traitors sometimes betray their human masters not because of money, but because their masters are unworthy, unfair and disrespectful. They tired of their human masters. Even if this idea looks like nonsense for our blood thirsty nature, but best fight is the one, that have not happened. If your enemy decided to surrender or become your ally, its best outcome.
Orcs are good at waiting when Barons castle protectors starts to starve.
Its important to make some save passages. So, if any of castle protectors leaves castle, throws away his/her sword, we, Orcs, should allow him or her to leave with peace. Humans knows it. It greatly demotivates castle protectors to fight until death. Sometimes, protectors of human castles surrenders their castles without fight, after few weeks of siege. Its worth notice, that we should show them Mercy. Dead human is feast for few, but living human can be good slave or even loyal worker.
If castle protectors are to stubborn, and we are short in time, we, Orcs, are good in digging. We dig underground passages and castle walls collapses. And, of course, we, Orcs are good at killing and eating knights. And other Barons usually hated each other, so, while we are making siege to Baron's castle, other ones prayed to their gods that we don't assault their castles. Barons unlikely to help their troubled kin. And its only matter of time when we siege their castles.
Sometimes we had really big fights with joined armies of few Barons. Its the time WarBoss-of-WarBosses helped. GodMother (via Shamans) explained him how to make Lines. Connecting things. It include art of making passages, art of sending scouts. How to send orders and reports asking Shamans to silently scream to each other. How to pay human traitors. Humans calls it Logistics, Tactics, Reconnaissance, Communication and Soft Force. So, we always was aware where humans are and what they planned, and we always gathered proper number of warbands at place required, so we nearly always outnumbered human armies. We had feast before fight, and humans was usually hungry and after long walk.
When fight begins, humans used archers - but we had big shields arrows cannot penetrate, and orcs skin is thick - archer had to be lucky.
Crossbowmans caused some trouble, but they are few, because crossbow is expensive to make and crossbowman needs lot of training to aim properly to land bolt in viewing holes in our shields. Yes, we, Orcs, are good at running in heavy armor while carrying our shields in front of us to protect from arrows, bolts and stones.
Pikemen was dangerous. Especially when they guarded archers among the fromations. But we find out we can throw big sticks and stones, bee hives (Bees stings cannot pierce Orc skin), or even jars with incredibly smelly lavatory contents to distract and demoralize pikemen and archers formations. Later we used slingers or portable catapults like this one, which are easy to install, pickup and use in other place
When humans send Knights on horses with long spears, we used our bear sticks. They are longer than spears. If you put one end of bear stick to ground and point sharp end to Knight's horse, horse usually has it chest pierced, and its easy to stomp to death fallen knight with our metal cowered boots and maces. No mater, if our weapons cannot pierce through plate armour, if we bend armour enough, knight inside will die.
If human send heavy infantry, we usually surround and crush them. Swords are not effective against us. Our skin is thick, our armours are bulk and heavy, shields are big and we can pick and throw stones. And we use big and heavy axes and maces majority of adult human cannot even carry in hands. So, even handfull of orcs can deal with few dozens of heavy infantryman without aid of archers and knights.
There were also stories and few cases involving either spellcaster humans, or heroes with magical weapons, capable of killing orcs single handed. But, this stories are probably tales. Barons hires Bards to tell this tales to motivate cowardly knights to fight. In reality, it was little problem. We found few rune cowered swords that "slice easily and gives me more strength and endurance" or found knight in "magically enhanced armour", we cannot either break this armour, or disassemble it, or harm human inside it in any way, so we had to simply drew this knight in improvised warband lavatory.
Majority of spell casters can only make tricks to entertain peasants to make them share food with spellcasters. Yes, there was few spellcasters capable of throwing fireballs big enough to burn castle to ashes. But they can throw maximum few fireball per day (and they had to eat rare magic mushrooms, perform fasting and meditations for week to gather enough mana to make spells), and they was mainly hired by Barons to burn each others castles. The only documented case of usage of magic in Humans to Orcs was was performed by Durga, 21th Warboss-of-Warbosses. She seduced and hired one of this spellcasters to break fortifications of King Roland The Grumpy. It was much faster, than making siege to King Rolands castle. Furthermore, when humans invented boom sticks, spellcasters become obsolete. Using boomstick and boom powder was much cheaper than hiring spellcasters, and spellcasters became obsolete. Few become outlaws, and their trade was forgotten.
Human healers has "magic that was more effective than medicine in healing." But this magic can do nothing when properly beaten knight looks like blob of bent armour with flesh and bones insight. So, this healers was mainly hired or forced to heal Orcs, and, when Shamans learned their trade, they become obsolete, they only had trade as travelling healers and herbalists to heal various old man illness of peasants, and receive payments in food.
We had few naval battles too. We used really big ships our human slaves and hired craftsman build for us. We used long paddles to make them swim fast and ram humans ships.
Sometimes humans used big boom sticks. But it was pathetic. Boom stick is build to ruin castles. We don't build castles. And our warbands do not attack in well organized battle orders, so even if you manage to kill few Orcs with with boom stick blast, other Orc will not stop. And when you reload your boomstick, we will be close enough to tear your arms.
Sometimes humans send sneaky assassins and Death Monks with poisoned blades and dark arts of killing by punching special spots on bodies to kill WarBosses. Assasins usually was hired to kill rival Baron. They mainly succeeded. But it was ineffective for orcs. Because, we, Orcs are
physically attractive, and humans are not. Physically attractive orcs do not need fancy clothes and decorated armors to look awesome. And humans does.
Physically attractive orcs do not need solitude, if there is few dozens on orcs including Shaman and Warboss sleeping in one dinning room in castle, they feel comfortable, they don't need to hide from each others like humans do because they had ridiculous things like inferiority complex, body shamming and convenances.
So, even if assassin manage to sneak into sleeping chamber, he will have issues finding the right orc he was hired to kill. Orcs are physically attractive, so they all looks the same to humans. Also assassins will have breathing issues, because Orcs smell good, and humans do not.. Even if Death Monk manages to reach Warboss and press right point on his belly, Orc is unlikely to diy. Orc is not human, vulnerable place for humans is likely to be covered in few inches of body fat in orcs body. Because Orcs are physically attractive! Even if nearly miracle coincidence happens and assassin kills the right orc, its not an issue. Next morning Shamans will promote other Warboss.
There was few cases when Assassins was hired to kill shamans. But they never succeeded because, how can you sneak undetected to Shaman, who can hear ants talking under his bed, while he is sleeping? How can you
win fight with Shaman, if he is always surrounded by other ors? Even if Assasin catch Shaman when he is listening to Songs of GodMother in solitude, what can Assassin do against him or her? Shamans are guided by GodMother, they can dodge arrows, see invisible, hear silent, predict opponent moves, sniff poisons. Even senior age orc can outrun majority of humans. Assassins never succeeded in killing Shamans. And if after torture Assassins reveal name of person who hired them, the punishment will be fast, imminent and legendary. Killing Shaman is offending GodMother!
Humans learned it fast, that fighting us is hard. And because humans are cowards, they are not very eager to fight with us. And, here is our main, and probably, most powerfull weapon strikes! And, we, Orcs, showed Mercy. We spared live if humans surrendered to us, and we even allowed them become our slaves on long leash until they show their loyalty, and after it, they even was paid in gold trinkets according to work they have done. And sometimes we released slaves, and allowed them to travel to kingdom we want to conquer, to praise how our Shamans are wise, and Warbosses merciful to humans who want to willingly work for Orcs. So, in general human, do not wanted to fight with us. And best struggle is the one, that did not happened, even if this sounds like nonsense to orcs.
Later, we, Orcs, make clergyman work for us. Shamans explained them that our GodMother is Mother of humans gods too, and its ok for human to serve Orcs as masters. Its the reasons why we allow clergyman to perform their rituals and chants at their temples. They serve our purpose. In exchange,
we still allow them to have their secret pleasures and save some donations peasants pay to them.
- Orcs are strong, but they should not forget they are Orcs, not Humans. Humans are weak, but they are useful.
Right now, orcs has lot of human vassals, and few kingdoms still struggling with us. Probably, we should stop struggling with them and wait, when humans overthrow knights and will invite our WarBosses to protect them? Its not impossible, it happened in few kingdoms we conquered before. But what if Orcs become interested in shiny trinkets, tasty food, leisure and indolence? We learn to be greedy and lazy. We become unfair. We will become the same as Barons, and humans will sooner or latter overthrow us, like they did it before with knights. So, let GodMother guide our Shamans to explain things to us properly, and provide us with WarBosses-of-WarBosses when we are in need of them. And let our humans be well fed, protected from outlaws and barons and be obedient and hard-working. Also orcs should never forget things Humans educated them - including reading and writing, building roads, wagons and ships, and, mainly, showing mercy and being fair.
Orcs should never forget GodMother created both Humans and Orcs different. It was for reason, probably, to make both Humans and Orcs respect and help each other?