Akkaido is right under chain mail a gamberson(padded armor) was worn, also under plate mail.. plate also had chain in the exposed joints... and saying the invention of plate mail made the sword useless is a bit of a joke, as most soldier couldn't afford to wear maintain travel etc etc etc in plate mail.. the stuff is heavy, but well designed an doesn't limit your movement much surprisingly... but you get extremely hot wearing it thus cannot keep up a fight for long, or travel a distance in it. But yes a slashing attack of a sword against plate will most likely be useless so u thrust (with the pointy end) with the sword to penetrate the armor(yes i understand that most plate was angled to help stop this but its still possible). Plate mail is more vulnerable then chain(padded) against maces in the way that if the owner of said mace can dent the plate it stays that way so the person wearing it either cant breathe or move properly... or their head has a new shape.. i do viking re-enactment battle so i know a bit about this stuff but my knowledge on plate is limited ill admit... just my 2 cents... realism is fine but there is point were it becomes stupid to even try an achieve it.. an its a game realism can be ignored in most cases  ... sorry for the rant i cant get in-game atm... lol