+TheMasturCheef Bodkin arrows maybe? Bodkin arrows were "armor piercing rounds" and I'm sure they could penetrate plate armor. Plate armor (sorry if I'm wrong) had different thickness on "high risk" and "low risk" points and thickness was 1.5-3 mm. Long time ago, I was reading some old encyclopedia and there was this text "longbow could penetrate knights plate armor from as far as 160 meters". Now, imagine a skilled archer armed with longbow (real longbow, that tall one 🙂 ) and few bodkin tipped arrows. Bodkin arrow had pretty small impact point so the force that was hitting the was tremendous. But, there were good armors and bad armors (steels actually) as well as good and bad bows. I think we will never know the result of battle longbow vs. plate armor but I give my vote for longbow (bodkin arrow actually). Cheers!

@WankstaGhetto Of course, if it hits at the right spot on a not so late medieval full plate armour, it might penetrate! The truth is complex, as always.

There are reports from french knights from the battle of agincourt, that they had to tilt their heads forwards (like in windy, rainy weather) into the horizontal rain of arrows, because there were so many arrows shot! These arrows weren't shot from far away, they were shot from some dozens of meters away and precisely aimed.
We know that from the type of arrows they shot and from the reports.

This tells us 2 things:
1) Plate armour was almost invincible to arrows. The fact that these knights still advanced even though they were shot with dozens of arrows per minute must mean that they relied on their plate armour – and they weren't stupid.
But, they had to tilt their heads forwards because that way the arrows hit the top of the helmet from which they will simply glance off. The visor has breathing holes and sights, if you are hit by some dozens of arrows surely some of them will hit these holes and that means the whole force is transfered to your head and neck which is probably quite unconvenient, even if it doesn't penetrate and wound you, which is also a possibility.

2) Plate armour was not completely invicible to arrows as argued in point 1). Otherwhise they wouldn't have attempted to shoot at them.
Although they had to use dozens or hundreds of arrows to successfully wound a knight in such perfect late medieval plate armour, it still adds up if you shoot enough.

By the way, this is all just a short summary of things I heard in a video from @scholagladiatoria, where Matt interviews some guy from a museum (Toby something was his name I think).

I think that is probably a myth, 120 pound war bows are used at my local club pretty regular, in fact I shot with one a few days back, some shoot much heavier, as of yet I've not met a hunch back with bent fingers,

Plate penetration has been proven to be guaranteed at 20 yards or less. This is 60 feet away.

It will not penetrate at 200 yards which is where Longbowmen aimed for to disrupt the enemy at distance. Vollys of 6000 arrows raining down on the enemy did a good job of disrupting and dispersing the enemy. When fired at the side of a charging cavalry wearing plate armour, the weaker armour on the flanks of horses were pentrated with ease. Also the breastplate armour and the backplate armour of the enemy were thicker and in the main was impregnable, but joints, arm and leg plate were not. Remember though armour was not standard, it was made by different blacksmiths who used varing quality of steel and varying quality of "fit". Soldiers who gained weight since having their very expensive armour made still wore it despite the ill fit.

All videos you see are testing penetration of breastplate armour only. It is ridiculous to think longbowmen aimed for breast plate or anywhere else. Arrows were launched at 45 degrees into the air and hoped for the best. This is also never taken into account.

Ask any of the testers to wear their plate armour and have a 120Ibs Longbow fire an arrow into it from 20 feet using a hand forged bodkin arrow tip. None will accept the challenge and there is your truthful answer.

And yeah, a Crossbow is much more powerful at short range, but crossbows will not kill the enemy at 300 yards (⅓ of a mile). The bolts are not designed for long flight, are much lighter and at range does not have the same continued forward force of an arrow with a heavy arrowhead dropping from 200ft+.

@***** Nobody has claimed Longbowmen would be firing at targets at close range. They did not. After they finished dropping arrows at 300 yds in random place with the other 6000 arrows being fired at the same time, the Longbowmen took out their sword and joined the infantry.

The test against steel was just to see if ut was possible to penetrate. The test was at longer range and this range was reduced until penetration was achieved. Like you say this would not have been lethal. They carried on reducing the range and at 20 feet  the Longbow arrow penetrated the breastplate (thickest part) and would have stoped at the back plate.  Note all Longbowmen placed in the ground sharpened stakes beside them  to halt Cavalry horses. I presume there must have been times when they were still letting fly their arrows when the Cavalry were almost on them.  

On all subjects about Longbowmen, the topic always seems to be dominated by armour penetration. Longbowmen had the primary task to disrupt the enemy at 300 yards and these easily stopped dead the infantry and made all of them panic. When Cavalry were targetted, it was from the flanks and the taget was the horses. A volley of 6000 arrows landing in a cavalry charge would penetrate the weaker armour on the horse (weight had to me minimised by using lighter armour) and the legs. Felled horses would trip horses charging behind. Dismounted armoured Cavalrymen would be stampeded. An arrow hitting the armoured head of a horse would be traumatic to the horse without penetration.

Note I am not saying targets were picked out for archery shots. This would be ridiculous. The Longbows used had a draw-weight range between 60Ibs-140Ibs with the Average being between 90Ibs-120Ibs. I was told this personally by Professor Anne Curry who is the foremost expert in the UK for this period and who was the Chairwoman of Agincourt600 last year. 

The lower range weight would have been used by the younger longbowmen who had not yet developed the muscle and strength for the heavyweight Warbows. Archery and hunting which require accuracy are done using Longbows 55Ibs-60Ibs. These I think would be the last longbowmen in battle letting loose arrows and at close range.

There are eyewitness accounts of armoured Cavalrymen having a longbow arrow through the thigh and pinning it to the horse. There is no denying the Longbow was the weapon of choice for about 2 centuries.

The more powerful Longbows are no use at short range because the 6000 men would have to be shoulder to shoulder and that line would be too long. Otherwise they would have other Longbowmen in their way.

Once Infantry have engaged, no Longbowmen will be using arrows in fear of hitting their own men. They then join the battle with swords like the Longbowmen before them.

Every footsoldier was a longbowman, was trained from Childhood.

Before battle all Longbowmen took from a cart one bale of 24 Arrows tied together.  They got in place, put their cavalry stopping wooden stake in the ground and then place all their arrows in the ground around them.

Everything I know about Longbows and the Longbowmen at the time I learnt from Professor Anne Curry. I also own a self-yew Longbow with a draw-weight of 100Ibs.  This longbow is lethal. A 60Ibs Longbow is powerful enough to enter a charging hog up to its flectching and deer at 50ft. My longbow is almost double the power.

Crossbows would go through any plate armour at the time from 20 yards like it was butter. They were used by the French. However they were slow to load and useless at range.

The Longbow was also a naval weapon, something many people don't know. It's why the Mary Rose when salvaged had Longbows on board.    .       

Chainmail helped and if it was worn under plate mail it would be a useful added layer of protection against arrows. It is a lot of added weight. I have worn a cowl made of chain mail under a helmet and it was very heavy. A full body suit of mail would need a large strong man to wear it, especially under heavy plate armour. Cavalry horses needed weight to be minimised, It had its own armour, the weight of the rider, the weight of the riders armour and the riders chainmail. Those horse would be exhaused after a while. Some battles lasted all day. They must have compromised with the armour, like use lighter thinner armour, or less armour, etc. At Agincourt in 1415 the French had only about 600 Horse mounted armoured men, but 7000-10000 armoured men-at-arms on foot.

Longbowmen killed about 3000 of those armoured men, something the idiots in the videos don't know about while shooting their 30Ibs bow with weak arrows at armour. The rest of the armoured men were stuck in the mud, many suffocating because they couldn't push their heads up from the mud, their breast plates being sucked by the mud. 5000 of them were taken prisoner and later executed to stop them joining up with another part of the French army on its way to the battle. The English got lucky with the mud helping, but a victory is a victory and Longbowmen are given credit for that victory for a reason – anfd primarily against armoured men. The French outnumbered the English. Their armoured men even outnumber the English … and they lost.

That hole you mention in chainmail and armour would have been followed by infection from the arrow.  Most English casualties in the 13th Century in France were from disease. There was no doctors or nurses, no antibiotics, just illness, septicemia, gangrene and death.  Also in that time period people were dirty and didn't bathe which made it unsurprising.

When you see people doung their dumb tests on Youtube, bear in mind authentic arrows are £300 for 6. Do the people in the videos look like they can afford to waste arrows on tests. No they don't. They will have weak cheap arrow heads, weak cheap longbow, weak cheap arrow shafts, cheap fletching and armour which isn't an accurate representation of armour of the day. Armour also would have been tailored to individuals. A very strong muscular man will be able to wear thicker heavier armour. and weaker smaller men wear thinner and lighter armour.

If you want to read the most famous and accurate account of the Battle Of Agincourt, learn everything there is no know about a longbowman, crossbowman, armoured men-of-war then read the Agincourt section in a book called The Face Of Battle by John Keegan.  You will me an expert. You can smell the steel, blood and the fear during the battle as you read it. You will also learn about the preparations before the battle. Expensive compound bows of today are much more powerful than a Warbow, but I spent £1000 (about $1500) on a warbow because it is like holding a piece of history. When you have held and drawn a warbow, then read The Face Of Battle you will fall very deep into the story and feel lik one of the longbowmen.     

@***** I understand what you mean about the different factors needed for armour and not just thickness. Armour though was for protection from mace, sword, spears  and daggers. Armoured men usually joined battle after the infantry had engaged the enemy infantry. There would be no danger from arrows at this time because longbowmen and archers would not be using arrows anymore because their own men were there.

 Armour on shoulders and arms are smaller units and the shape is very round, so these factors stopped the armour needing to be thick. The chest and back though were larger areas and relatively flat and they protected vital organs. Heavy impact on armour would have still caused internal injuries from blunt force trauma and this is not something you want happening over the heart and liver.

Modern body armour is layered with different materials and it is lighter because of this and bullet resistant, but plate armour back then was made from the one material. Chest and back would need to be thicker because of the larger area. It's physics. If you jump from 6 feet onto a panel of steel 12"x12" bridging a gap there will be no damage. Jump from 6 foot onto a panel of steel 60"x60" bridging a gap and the smae thickness and same steel, it will dent and warp. The 60"x60" would need to be thicker.

Mail was effective against archers who used standard bows of about 40Ibs. Mail will have some resistance from a Longbow, but the KJ on impact would continue through the body and do damage. Mail over the head might stop penetration but a longbow arrow will have the impact of a heavy club and crack the skull like an egg. The same would happen with the breast bone (above the solar plexus) over the heart.  If a man punches the breast bone of another man, the punched man in about 20 seconds has difficulty breathing and the ribcage won't expand when trying to breathe, so imagine the force from a longbow hitting the spot, plus it would likely smash the breast bone.

I have worn the thigh pad used in American Football and had a mate swing a crowbar into it as hard as possible for a demonstration of it's toughness, But that pad won't stop a player breaking my leg if his shoulder impacts my knee, right?

Plate armour will protect from clubbing and slashing but not stabbing. Mail will resist stabbing but not clubbing and other impact forces. The two combined give an all round system.

Remember the armoured guys joined battle after arrows were no longer used because archers would be hitting their own troops. At Agincourt they went first only because they sensed easy victory and glory against the English. They wouldn't normally do it.

This is why armour design didn't factor arrow protection as important. Armoured men were mainly nobelmen and they were not usually engaged by regular footsoldiers.They were engaged by the enemy armoured men who were also nobelmen (all called Sir ,,,) or (Lord …), etc. After having their 'contest' in battle, the victor would take him prisoner, would treat him well after battle and ransom him.

This same kind of thing happened between the  RAF and the German Luftwaffe. Captured pilots were taken prisoner by the RAF and Luftwaffe, treated very well until the end of the war. 

@*****  Did you see the video in my previous response? That weapon will go through any armour whether round or not. Just click on the blue number in my comment under the video. It will take you straight to the part.

+Charlie The Turtle Longbow arrows were shot in the 1000s at a time. If you consider there were about 6000 to 7000 archers shooting several 100,000 arrows during battle, probability suggests the enemy is going to suffer some injuries/deaths. It is same principle as machine gun, multiple bullets, but only a few are only going to actually harm the enemy.

A 44 magnum can penetrate a 1,5mm armor plate but not a level IIIA bulletproof vest, at the other side a 60 pounds modern compound bow with a medieval bodkins point broadhead can penetrate the same bulleproof vest as butter, compounds (pulley bows) perform twice the power of traditionals (recurve, flat, composite, long, selfbows) so a 120 pounds longbow would do the same than a 60 pounds modern compound to a modern bulletproof vest.