To start, I am not flaming anyone here. The eastern style composite recurve bow was incredible powerful. Surviving examples have been found to have a draw strength of upwards of 160 lbs. Compare that to the 80-140 lbs. of the Welsh longbow. Mounted archers carrying these weapons were an even bigger problem. Notably the Parthians were a difficult bunch. The 'Parthian shot' consisted of a mounted archer firing an arrow straight back over the rear of his horse at relatively close range. This presented a very precarious situation for a heavy Roman infantryman with two pila and a short sword. Mail presented decent protection against the arrows and bows of the northern barbarian tribes as they were of the typical European design (no recurve and usually made of a single piece of pliable wood with arrows that were meant to kill/maim rather than penetrate armor). This isn't to say that the barbarian tribes weren't dangerous or even relatively technologically advanced, just that more advanced missile development techniques were not available to them. On the other hand, the Eastern empires had the benefit of greater wealth and the access to advanced bowyer techniques (mainly due to mounted nomad tribes). Combine the cash and technological inovation/flexibility of an empire like Rome with a deeply ingrained archer tradition and hopefully you begin to understand what I'm talking about. The mainly Celtish/Briton tribes of western Europe strongly favored the sword and shield against which mail fared quite well (as far as I know, Rome adopted mail from the Celts). Even the Germanic tribes armory could be mostly countered by mail with the exception of the heavy axe. It wasn't until meeting the falx in eastern europe and later on the composite bow, that true armor change was initiated. It must be said that armor was not always meant to just stop injury, it was also expected to stop skin penetration as infection was probably alot more dangerous than a broken bone. I'm not sure if the easterners had bodkin type arrows but taking into consideration that most of their archery was adapted mainly for war and not just hunting, I suppose it's possible. Consequently, mail was rendered less effective than armour that could be made to deflect such attacks and it was a heck of alot heavier than segmentata. As far as mail during the Crusades, it was 800 years after Rome's fall and mail armor had evolved, not alot, but it did evolve. Double mail was common during that time as far as I know and and was just as flexible as regular mail and offered better protection, but it was even heavier. Feel free to diagree as always.