Firstly, I’m not convinced by the argument that they invented plate armour just because they had a clothing with a different purpose to sew it in. Additional armour is a burden and I think there was a certain incentive necessary, at least a mental one. And the opinion that it had something to do with the more common use of the composite crossbow or the increase of use in archery in the 13th century in general does not sound so bad. Couching on the other hand was common from about 1100, so it’s for me a worse argument. Yesterday I read that there are some hints that the use of coat of plates started in eastern Germany. I think that such hints are not relevant but just coincidence, but it would be interesting to speculate about the impact of Mongol archery during the invasion of Europe. However, the word has been used, it’s all just speculation, so different opinions are usual and should be accepted.
Some data for projectiles:
1. Arrows from a longbow: the background of the test was to evaluate the range of bodkin arrows and the performance of different arrows. Most were shot by an angle of 40 to 45 degrees from a 150 lbs wooden longbow (yew), some in addition from a 170 lbs fibre-glass flat bow. I only give some data of the lightest and the heaviest arrow from the longbow. The data is averaged from several shots.
range initial energy energy at 200 m
Arrow 53,6 g: 315 m 111 Joule 60 Joule
Arrow 95,9 g: 230 m 134 Joule 78 Joule
(Edit: there is something wrong with the editor, I cannot bring the data beneath the correct row. I hope you can read it nevertheless.)
Modern armies differ in the thoughts what energy is necessary to put a warrior out of fight. In western armies 80 Joule is the most common value given for an unprotected person. That’s a very theoretical value of course. The second arrow had that energy at 180 m.
We see a very small loss in energy over a long distance, in complete contrast to firearms (at least black powder firearms). When the historical data is put together with reconstructions and tests, it appears that the most common arrows for late longbows weighted about 100 g and had to be shot from bows over 120 lbs to achieve the reported performance (that is for example that practice shooting with bows at distances below 240 yards (219 m) was discouraged by advice in the Tudor times). So the data of the second arrow might be close to the historical performance.
(Source: “The Great Warbow”, by Strickland/Hardy, 2005, mostly pg. 408-414)
Some data to compare:
2. A reconstructed composite recurve bow of late antiquity and eastern origin (Sassanids) with a draw weight of 80 lbs achieved with the usual 50 g arrow a range of 188 m and an initial energy of 62 Joule. That energy an arrow from the 150 lbs longbow had not at 10 m, but at 200 m!
(Source: „Die Reiter Roms, Teil III, Zubehör, Reitweise, Bewaffnung“, by M. Junkelmann, 1992, pg. 162-173)
To get some impression what the "energy" means at all: a very experienced fighter can achieve an energy of about 130 Joule with a fist stroke, if using the whole body weight behind it. You know, often persons cannot be knocked out with this energy. The stroke with an 1 kg weapon with one arm achieves an energy of about 65 Joule, an 2 kg weapon with both hands of about 130 Joule. The thrust with a 4 kg polearm achieves about 50 Joule, with a 800 g light lance about 30 Joule. Used from a galloping horse the 800 g lance would have an energy of 160 Joule and an impressive penetrating power considering the weight behind it, wouldn’t it be an elastic stroke. The heavier lances used with a lance rest would have been terrible weapons (but perhaps one-time weapons).
We see, hand held weapons are low energy weapons, that’s the reason why bladed and pointed weapons were usually used in war.
3. Modern stronger compound bows are in the range of 60 to 100 Joule initial energy.
4. Arquebuses of the 16th century (late 15th c. guns were not much different) shot projectiles of about 20 to 30 g with an initial energy of about 1500 to 2700 Joule. The energy depended on the amount of powder used. 18th century muskets shot bullets of about the same weight and the same energy. A test with a 16,6 mm caliber 18th c. musket with a 26,7 g bullet showed the following results:
Initial energy 2764 Joule, energy at 200 m: 671 Joule. (The energy is thought to be higher than originally achieved because modern black powder was used in the test). We see a dramatic loss in energy at distance, however the energy is still much higher than what any bow or crossbow could ever have achieved. But we have to take in account that a fat lead bullet needs a lot more energy to penetrate than a needle pointed arrow (a question of energy density, I don’t want to discuss this here).
5. Modern guns achieve initial energies of about 3500 Joule for a medium rifle bullet (f.e. .308 Winchester) or 500 Joule for a medium pistol bullet (f.e. 9 mm Luger or .45 ACP). Of course there are much stronger calibres, a 12,7x99 bullet from a .50 cal machine gun has an initial energy of about 16500 Joule and 6500 Joule at a distance of 1000 m. A .308 Winchester bullet with an energy of 3273 Joule and a weight of 10,9 g has an energy in 200 m of 2345 Joule and in 300 m of 1966 Joule.
(Sources: mainly “Weapons and Warfare in Renaissance Europe” by B.S. Hall, 1997; “Geschosse Band 2: Ballistik, Wirksamkeit, Messtechnik” by B.P. Kneubüehl, 2004; “Wundballistik” by Kneubuehl, Coupland, Rothschild, Tali, 200