What weapons could an Iron Age society wield that would be effective against Medieval (High Period) knights?

Question

In numerous fantasy worlds, including my own, I have seen knights battling what appear to be "barbarians" inspired by the Celts, Germanic groups, or possibly some Scythians. From what I've seen, the horde is axe heavy, but I feel that a battle axe would be ineffective against an armored knight. However the horde must be a threat even if the weapons they wield are untraditional.

What weapons could an Iron Age society (preferably Germanic) wield that would be effective against the traditional knight?

Note: I'm looking for infantry weapons because one of the advantages of the Germanic tribes vs the Romans was the Germanic cavalry (or lack thereof for Rome). Knights are probably far better than Germanic cavalry.

The knights would be equipped much like their historical counterparts (1000-1250AD)

The barbarians would be armed much like the Germanic hordes (Goths, Vandals, Lombards, etc).

The "Hordes" arrive approximately every two generations from the northern passes. The quality of the horde varies some are raiders, some are refugees, and others are war bands that settle in the frontier.

Answer 1

If the knight is standing on the ground (as opposed to sitting on his horse), he will be much easier to kill, and if he is lying on the ground, it is even easier since the weight of his armor will prevent him from getting up. Easy ways of knocking a knight off his horse with iron age weaponry are:

• Hit him with a big rock
• Lasso him and pull him off
• Kill/wound his horse
• Make the horse buck him off
• Trap his horse, forcing him to get off
• Set him (or his horse) on fire

Have a set of catapults included in your armies. Also, setting up a rock avalanche on a mountain next to the battlefield to be triggered when the knights are in the way would be beneficial.

Using a lasso is self explanatory.

A spear would be useful for killing the knight's horse since you don't have to get to close to the knight. Archers and javelin throwers would also be useful, but the archers probably wouldn't do much against the knight himself. Another way of stopping the horse is the use of caltrops would impede the travel of the knights and could be useful in battle. Similar to the dirty trick of throwing sand in your opponent's face, your soldiers could have a pouch of caltrops to throw under the horse's hooves.

Getting the horse to buck the knight off would be tricky. Horses are generally afraid of wild animals (especially carnivores), so setting loose a pack of wolves into the knights should cause plenty of mayhem.

Trapping a horse is not difficult. Rough terrain, such as on a mountain or in a forest, would provide natural ways for a horse to get stuck, so these places would be your ideal battle grounds. Also, digging deep trenches in the ground would create a problem similar to a cattle guard. The typical pit-covered-in-branches would also come in useful here.

Fire would be very useful, not only because it scares horses, but because it can kill things with armor. Use flaming arrows for your archers, and have lots of torches and things that make fire.

To kill the knight once you have rid him of his horse will be much easier. An axe should be good enough to cut through his armor (like @Alexander said). Spears can also go through armor if they are thrust hard enough. Rocks will also come in useful. Hitting the knight in the head with a big rock will most likely dent his helmet, which will dent his skull, which will not be good for the knight. If something sharp can get through a crack in the knight's armor (such as the visor), it will also do severe damage.

Answer 2

War hammers have pointy ends expressly to penetrate mail.

Two handed mass weapons like Mattocks and Pole-axes are effective against heavily armored knights, since they move more slowly than lightly armored troops and are less able to dodge out of the way. The weapons devastatingly heavy blows can break shields and crush mail resulting in broken bones and pulped flesh.

Answer 3

TL;DR: big tech level differences and anachronisms are not stable. Your "barbarians" will either end up with medieval-style weapons and tactics and a suitable society needed to support them, or they'll be crushed, or they'll be an irrelevance.

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So, obviously, military technology improves given a few hundred years. Better weapons, better armour, better horses with stirrups and horse shoes and their own armour... all these things give the more developed army a big advantage over the less developed one. There are perhaps other, less obvious things, like improvement in medical care (not much in this case, I suspect) and improvement in farming and nutrition, which will help produce tougher, healthier soldiers. Better construction techniques give better fortifications. Better engineering gives better siege weapons. Better boats lead to better logistics.

Your "barbarians" are clearly at a huge disadvantage if they try to operate on foreign soil... maybe they have some home advantage, but if they have farms and settlements they're very vulnerable. They know this. The medieval society (or societies) know this.

Those war hammers, flangeds and spiked maces, and various things like bec de corbin that are designed for fighting armoured oppoents? They obviously won't have them, or even consider them to be useful before they've fought the sort of people they were designed to be used against. Assuming they're not slaughtered promptly though, they'll start getting them. You've hopefully not created a planet of hats (and if you have, hang your head in shame), there isn't going to be "the medieval country" and "the barbarian tribe". There will be many of each, and some will fight, and some will trade. Your "barbarians" will learn about the design of weapons to pierce and crush armour, and how to get them. They'll learn about use and creation of armour. They'll get better horses, and improved tackle for them.

In due course, they'll be well equipped to fight the medieval-level opponents, because they'll have pretty similar kit all of their own. You'll miss the style of topless greatsword wielding conan-alikes in fluffy hotpants, but on the other hand you won't get to see your conans all shot to death with crossbows, ridden down by heavy cavalry or beaten and hacked to death by better armoured opponents. If you can't beat em, join em.

There's no secret weapon or magic technique that'll let them stay the same and come out victorious, unless your universe literally has magic and your "barbarians" aren't adverse to using it. You wanna deal with heavy cavalry? Then look at how medieval warfare evolved... Lansknechts, Swiss Pikemen English Longbowmen, Geonese Crossbowmen and the like. A cursory glance at a short list of infantry vs cavalry techniques in the middle ages might give you what look like some ideas, but the infantry in question are moderately well disciplined and equipped medieval soldiers that aren't really equivalent to the folk who fought against the Roman legions.

edit I have just remembered the "gallowglass", which apart from having a pretty bad-ass sounding name are often imagined as a big guy in a kilt with double-handed sword, like a sort of conan for colder and wetter climates. The original gallowglasses were even descended from vikings. Don't be fooled though; those guys were well equipped and had high-quality armour. Not simple steppe warriors!

Answer 4

Axes are actually pretty smart weapons against armor. Although against truly solid armor you are best off with blunt force weapons like maces, halberds, flails etc.

The reason axes are good is because they work kind of like a club with a sharp edge. The circular nature of the axe means all the force goes in a small sharp area of the axe, allowing for maximum cutting power. If the armor is strong enough to withstand this force the blunt club-like force of slamming an axe into them will still be effective... assuming the soldiers arent outmatched in training and cohesion as well as armor.

Also if you have the high ground against opponents that are that heavily armored they'll be dead tired unless on horseback. Simply maneuvering for extended periods of time and forcing the armored foes into countermaneuvers to tire them out will also help even the odds.