Numbers win wars. One presumes based on most settings that goblin armies are simply easier to maintain per man. Larger troop numbers allow a force to engage in tactics that are much more destructive/maximize killing power such as Pincer moves.
I'd argue that it is Logistics and Strategy which are often more important in determining who wins rather than sheer numerical advantage. (But It certainly is a factor!).
The Overall Logistics affects your strategy, and your overall strategical outlook affects your tactical considerations going forward.
Julius Caesar's Gallic wars, in my opinion, is a good example of Roman logistics and strategy triumphing over numbers. Pulling off this campaign would be a very hard feat without proper logistics, if not impossible. (Unfortunately, said Book can also be rather dry were reading material is concerned...)
The goblin is most dangerous on a unit level, where their natural organization hierarchies make them more dangerous in concert.
I'd argue this point, but more from physicality than any hierarchy. At least concerning formations from a 'Unit' basis (I am not sure exactly how you would specifically define a unit). Smaller stature and physical prowess will play a factor in formation fighting. They might be able to have more men in a given 'frontage', but this wouldn't play that much of a factor as you might think. Their smaller size means that their range would likely be lesser (Even when using spears)... and this is quite important.
Though their small size does mean that it is less likely for a human-sized adversary to score a direct impact to the legs and feet (And if Goblins use shields, most strikes would be glancing or deflecting blows), their head would likely be more exposed. I think this should be taken into consideration.
The Goblins could get away with using longer spears/pikes... but then this could theoretically prove to be more physically taxing... and this can be detrimental over an ongoing battle. I have acquaintances online who have experience with pikes. They can be more physically demanding than you might expect, more so than with spears. Pikes are essentially a long wooden lever with a weight on the end, so in short this is not something you want to be holding out all day. Spears can be similar, but are smaller and lighter and thus take less strain to use.
Now, if you had some Chad Gobbo's with raging Arm muscles and bulging thighs and they can use pikes. That's something to consider!
Armour can also play a big role in determining how battles from formations can ensue. If both sides largely have shields and spears, both formations will go about battle cautiously, and from the battle-furrow (My term for the middle-ground, which is a space about a metre or two wide between two formations), spears and other long weapons will only slowly be brought forward to-and-fro, and most offensive action will be generally be made from caution. Shields will render most attacks that do land on an opponent will generally occur as an indirect (Either from sliding or from a draw-cut as the spear is drawn back) or glancing hit, and death is not very likely. Battles therefore would be rather bloodless until either one side routes, and most battles would likely last for around 5-10 minutes and then one or both sides would withdraw momentarily for a breather before the formations would return and begin attacking again. This has been called as 'pulse fighting'. It can continue on for hours, or until a gap or similar occurrence arises within one formation or another and is potentially exploited, this can cause a rout to occur. When a rout occurs, the routing side will then suffer the most casualties. Pulse fighting makes sense to anyone who has experience with martial arts.
(Having more frontage in this case might actually be an advantage, they can press more weapons into service depending on how they fight, however the fact that their heads are likely a more exposed target by the humans is cause for concern)
However, if you have one side that is heavily armoured and the other is not as well armoured (Lets say, the Humans are well armoured and the goblins are not as well armoured), then things change. Well-armoured troops are not as afraid of being struck as lesser-armoured troops, and thus they can attack more ferociously and with more force. This means that battles will likely ensue more quickly. Battles will still likely be postponed so that everyone gets a breather, but I'd wager that the not-as-well armoured side will be rout much quickly over the course of the battle. (The battle of Wisby comes to mind for this.)
Once everyone starts wearing heavy armour, things change again. Battles likely become more slower-paced again, weapon-choice will tend to favour polearms over spears (Or pikes over spears). When it comes to heavier armour components, you often need greater momentum in order to bypass these defenses (Either to perforate through an armoured surface, or less-importantly, to penetrate through an armour via blunt-force, which is a more unreliable way to damage someone through armour). And so Polearms are an ideal weapon. Daggers can also be ideal for going through gaps in an armour, which is why Harnishfechten (Or Harness fighting in German) often incorporates grappling moves for downing a knight so that they can be stabbed through a weak-point with a dagger, poleaxe or similar weapon. Shields also tend to be dropped in favour of two-handed weapons. This is an important consideration because power-generation is often of more importance when it concerns driving a weapon home against plate armour and actually doing anything to the person inside. The defense that a shield comprises compared to plate armour often means that in most cases a shield is rendered redundant except against oncoming projectile fire.
This is where my concern about Goblin physicality comes into play. Weapons that have the capability to cause damage through plate armour tend to be heavier. This can put more of a strain on a goblin force. Combine this with armour, and this strain will only increase. So whilst during the initial battle they could be fine, after a period of time they will likely fatigue quicker in an engagement and will likely need more 'breathing' periods.
In pretty much most circumstances, I don't see this going well for a Goblin force, formation-on-formation, because of the size, potentially strength and potentially the reach advantage that is more likely to be attained by Human forces. This is, however, an observation that is entirely dependent on how closely to historical accuracy that Seeds of Chaos wants to set itself.
If a goblin army can constantly maintain larger forces, and can replenish these lost numbers compared to Humans, than that is also an important factor! It doesn't matter if you can kill three times as many Goblins if they can replenish again within a year and attack you again with the same numbers.
But either way, I feel that they will be weaker in most circumstances.
Ahem... time for a Line break (And a dinner break)... one moment.
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Ranged
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I feel that the Goblins would be better served by having a good ranged component in their armies, given that they can field larger armies, it would be good if they can utilize a fair proportion of that as being composed of ranged troops. This would also pair them well with the Orcs, who otherwise excel in physical prowess but are not great at organised formation-fighting. Ranged fire, if employed properly, can soften up a formation over time. This could prove vital for an Orcish charge. As to their ranged weapons, I can only see three potential weapons. Crossbows, slings and javelins. Slings and javelins can be used with bio-mechanical advantage, so even with less physical strength they can still use these weapons efficiently. Crossbows would also be viable, both because the weapon can be spanned by mechanical means, but also because the powerstroke between a Goblin and a Human crossbow should be similar. This means that a crossbow can be made short whilst still being as powerful as human-sized heavy crossbows. (It would surprise most people, but most powerstrokes of Heavy Medieval arbalests were short, only about 4-6 inches. This surprises many people.)
Bows, I don't really see Goblins using efficiently. Bows can require a lot of physical strength in order to use properly. If they were to use a bow, I'd imagine that a short composite bow would be best. I don't see them using self-bows efficiently, largely because the size would be a concern (Unless they were to design a form of asymmetrical bow).
Range-wise, I predict that Goblins could easily hit the 200 metre range from long slings (Probably with stones/clay projectiles about ~50-80 grams). They could probably shoot as far with their crossbows but by then the projectiles would have lost most of their energy in comparison to a slingstone. For javelins, I'd guestimate ~40-50 metres from a run-up, but from a standing position their range would likely drop to around 20 metres. Using an amentum or throwing strap, you might be able to increase this distance from a run-up throw.
Effective ranges change depending on the armour of the enemies they are facing. If they are facing heavily armoured troops, then slingstones and crossbow bolts will likely only be effective out to ~20-40 metres. Same with javelins. Against relatively unarmoured Humans, I'd say about ~100-120 metres for goblin-sized slingstones, about ~80-100 metres for crossbow bolts and about 40-50 metres for the javelin. Slingstones tend to lose their energy at slower rates compared to arrows or bolts because they do not have fletchings which sap their energy.
If the Goblins decide to go down the Roman/Greek route, Lead glandes are one of the more aerodynamic projectiles (High density + Low surface area + Slower-than-firearm velocity = Not much form drag and low skin-friction). From my understanding, they only lose 1/10th to 1/8th of their energy at the end of their flight. And they could probably get to a range around ~300-400 metres with them. Effective range? Armoured, about 40 metres, unarmoured? About ~200+ metres. (This is pretty much what Xenophon states in his Anabasis against unarmoured Persian archers and slingers)
I don't have any specific information regarding crossbows or javelins, but I do have the Israeli medical journal about Slings and their associated trauma... and they cite similar ranges regarding damage potential as I've put down under "Effective" ranges.
I think that outfitting a proportion of Goblins as ranged troops would be an advantageous way for them to fight. And I feel that It would make them more dangerous overall if they incorporated them in their way of fighting. For one thing, Pincer movements would be greatly assisted if you have ranged troops shooting the shit out of the enemy flanks before committing the flanking Gobbo's to charge. Or, you could create a specialized force of Flanking Gobbo's armed with Javelins, who throw said javelin from running (Which increases the range) and then close in to the enemy flanks with any specific weapon you have in mind. Even if the enemy is wearing plate armour and the weapon does not penetrate (Or glances off), a thrown javelin still has a fair amount of momentum and so you could periodically shock or stun someone for a few seconds.
Orcs are scary for really easy to understand reasons. They're big and strong, can smash shields, and have bodies that can take far more punishment then lightly armored humans. If you stuck a human in a fight with one, it would end poorly for most humans. But, many of the same factors that make orcish armies bad matches for human armies are the same problems human armies have against goblins. Numerical superiority, cooperation among units, etc.
Ohohohoh, I don't doubt it!
Orcs would frankly be "Shit-in-pants fear inducing". As I have said before, I cannot begin to comprehend the legitimate danger that Orcish weaponry would impose on a battlefield. Orcish ranged weapons would be legitimately terrifying. Nobody teach them how to use the bow or sling!
Thankfully, the Orcs seem to be a more down-to-earth melee brawler 'Gung-ho' type. Which is where Human formations would probably fuck them over.
Attacking a formation as an Ad-hoc group of tall dudes haphazardly rushing up, that's asking for getting ganked by guys with polearms.
Now, imagine a plate-armoured orc. Or better yet, a thousand of them. Fuck that! Fuck that 1000x if they also know how to fight in a formation also!