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Effectiveness

Mail's resistance to weapons is determined by four factors: linkage type (riveted, butted, or welded), material used (iron versus bronze or steel), weave density (a tighter weave needs a thinner weapon to surpass), and ring thickness (generally ranging from 1.0–1.6 mm diameter (18 to 14 gauge) wire in most examples). Mail, if a warrior could afford it, provided a significant advantage when combined with competent fighting techniques.

When the mail was not riveted, a thrust from most sharp weapons could penetrate it. However, when mail was riveted, only a strong well-placed thrust from certain spears, or thin or dedicated mail-piercing swords like the estoc, could penetrate, and a pollaxe or halberd blow could break through the armour. Strong projectile weapons such as stronger self bows, recurve bows, and crossbows could also penetrate riveted mail. Some evidence indicates that during armoured combat, the intention was to actually get around the armour rather than through it—according to a study of skeletons found at the battle of Visby, Gotland, a majority of the skeletons showed wounds on less well protected legs. Although mail was a formidable protection, due to technological advances as time progressed, mail worn under plate armour (and stand-alone mail as well) could be penetrated by the conventional weaponry of another knight.

The flexibility of mail meant that a blow would often injure the wearer, potentially causing serious bruising or fractures, and it was a poor defence against head trauma. Mail-clad warriors typically wore separate rigid helms over their mail coifs for head protection. Likewise, blunt weapons such as maces and warhammers could harm the wearer by their impact without penetrating the armour; usually a soft armour, such as gambeson, was worn under the hauberk. Medieval surgeons were very well capable of setting and caring for bone fractures resulting from blunt weapons. With the poor understanding of hygiene, however, cuts that could get infected were much more of a problem. Thus mail armour proved to be sufficient protection in most situations.