The Woldan wrote...
Wrong and wrong.
Hits from bastard swords and two handed swords could easily penetrate chainmal and the blades still had enough power to cut the arm completely off. A large sword and a strong wielder could even defeat platemail, the only way to be truly safe from a big blade is wearing a full plate armor with good angled plates.
The chainmail also offers poor protection from ''stabbing motions'', spears, longbows and especially crossbows could penetrate it easily.
It was cheap, it offered some protection and was widely available - thats why it was so popular.
It is impossible to cut or slash through maille, even with the larger swords. That is the entire point with the armour. A axe could possibly hack it's way through it, but it'd have to be repeated blows against a rigid structure. It does not however protect well against the force of the blow, so while your arm won't be amputated... it will still be broken.
However, most fighting styles are all about going around armour. In the massgraves outside Visby, Sweden, there were hundreds of people buried in their maille. All having their wounds in their faces, their legs or hands... were the maille would not cover. Not one had melee injuries on the torso.
As you say however. It makes poor protection against stabs. That's where padding comes in however. It is good against stabs and thrusts. The brigandine, a combination of padding, maille, padding, was the primary armour of the knights at the crusades are practically unpenetrable (insanely hot and could not cover joints though).
Oh... and maille was anything but cheap. Comparatively, maille and plate is almost as expensive. Plate replaced maille at the start of the renaissance and onwards. Once it started to show, maille got phased out. Maille was aslo useless against firearms, which is why it got replaced by plate.
Defeating someone in plate is about the same as defeating someone in maille. Go around the armour, attack weak points like armpit, face, neck, knees, trip them or punch through with a spiked polearm.
Also... twohanders and "bastard"-swords and maille are not contemporary. Twohanders are renainssance weapons, the time of pike, firearms and plate. They showed up as maille started to get phased out as a means to combat the pikes.