The gambeson was padded textile armor worn alone by some fighters and beneath mail or plate by others.
The gambeson is a quilted textile defence: layers of linen or wool stitched into channels and stuffed with tow, wool or rag. It was worn under mail and plate by those who had them, and worn alone as the whole of a man's armour by the far greater number who did not.
It is the most widely worn armour of the Middle Ages and the least represented in museums, because textile rots where iron only corrodes. Almost the entire surviving record of medieval armour is metal, which quietly distorts the picture of what medieval armies actually looked like.
It was also indispensable to everything worn over it. Mail without padding transmits the full shock of a blow, and plate without an arming garment has nothing to hang from and nothing to cushion it, so the gambeson is not an alternative to metal armour but its precondition.
Construction is quilting on a serious scale. Two layers of stout cloth are stitched in vertical or diagonal channels and the channels stuffed, and the number of layers varies enormously — contemporary references run from a handful to thirty and more, which is the difference between a padded jacket and a genuinely arrow-resistant garment.
The stitching is structural. It holds the stuffing in place so it cannot migrate and leave a thin patch, and the direction of the channels shapes the garment to the body — which is why surviving quilted garments show channels running with the lines of the torso rather than in a plain grid.
An arming garment made to go under plate is a more tailored object again: shaped to the body, fitted with arming points at shoulder, elbow and waist so that plate defences could be tied directly to it. The pourpoint of Charles de Blois, made about 1364 and now in Lyon, is the outstanding surviving example of that tailoring.
Layered textile is genuinely effective against cuts and surprisingly good against arrows, because it defeats a projectile by absorbing and gripping rather than resisting it. A point that would punch through a single thickness is slowed progressively as it drags through successive layers.
It was the ordinary armour of ordinary soldiers. English assize legislation of the twelfth and thirteenth centuries defines equipment by wealth, and for men below the mail-owning ranks the required kit is a padded coat, a helmet and a spear — which is a fair description of most of the infantry in most medieval armies.
Beneath metal it is doing the work no one sees. It spreads the load of a mail shirt across the shoulders and back, keeps rings from being driven into the skin, and absorbs the concussion that mail transmits — the difference between a bruise and a broken bone.
Its strengths are cost, availability and comfort. It could be made by a tailor from materials any town had, repaired by anyone, and worn all day. For the price of one hauberk a lord could put padded coats on a great many men.
Its limitations are the thrust and the weather. A determined point will find its way through textile in a way it will not through plate, and a soaked gambeson becomes enormously heavy and takes days to dry — a serious matter on campaign, and one contemporary writers complain about.
It also burns, rots and wears out. Everything that makes it cheap makes it perishable, which is why a garment worn by the majority of medieval soldiers is now known chiefly from images, wills, inventories and a small handful of survivals.
Padded defences are ancient, and quilted garments are attested across Europe well before the twelfth century, but the gambeson becomes prominent in the written record as mail becomes general — the two spread together, because each needs the other.
Through the thirteenth and fourteenth centuries it develops in two directions at once: heavier, thicker coats worn alone by infantry, and lighter, closely tailored arming doublets made specifically to carry plate.
That second line outlives the first. As full plate matures in the fifteenth century the arming doublet becomes a precise piece of engineering with points and gussets positioned to hang a harness correctly, while the thick standalone gambeson gradually gives way to the brigandine and the jack.
Terminology is a thicket: gambeson, aketon, pourpoint, jack and doublet overlap across languages and centuries, and the same garment can appear under several names. Any tidy modern distinction between them is a scholarly convenience.
Surviving examples are countable on one hand. The pourpoint of Charles de Blois in Lyon is the best known, and it is a courtly garment rather than a battlefield one, which means the most-studied surviving quilted defence is not typical of what most wearers had.
Everything else comes from images and documents — effigies, manuscript illumination, inventories, and legislation specifying who must own one. It is a rare case where the written record is far richer than the material one.