The surcoat was a textile garment worn over armor, strongly associated with heraldry, crusading imagery, and knightly display.
The surcoat is the textile garment worn over armour from the later twelfth century to the fourteenth: a sleeveless coat, generally reaching below the knee and split for riding, belted at the waist and frequently painted or embroidered with its wearer's arms.
It protects nothing. Cloth over mail stops no weapon, and the garment survives in the record not because it defended a man but because it identified him, kept the sun off his armour and kept the rain out of it.
It is therefore best understood as part of the heraldic system rather than the armoury. The surcoat, the shield and the crest carry the same devices for the same reason, and the phrase "coat of arms" is a direct memory of the garment.
The basic form is simple: two panels of linen or wool joined at the shoulders and sides, sleeveless, open at the neck, with splits front and back so it falls either side of a saddle. Fit is controlled by a belt rather than by tailoring.
Decoration is the expensive part. Arms were applied by painting, by appliqué in coloured cloth, or by embroidery, and a great man's surcoat could be silk, lined and richly worked — closer to court dress in cost than to military equipment.
Length and cut change steadily. The long thirteenth-century surcoat gives way to the shorter, tighter cyclas and then to the closely fitted jupon of the later fourteenth century, which is padded, shaped to the breastplate beneath and no longer a loose coat at all.
Its practical functions are real but modest. Cloth over mail shades the metal, which matters considerably on crusade, and sheds rain, which matters everywhere — wet mail rusts fast, and a surcoat is easier to dry than a hauberk.
Its serious function is recognition. Once the great helm closed the face there was no way to identify a man except by what he displayed, and the surcoat put his arms on the largest available surface at exactly the moment that problem became acute.
It also carried allegiance rather than just identity. The military orders are the clearest case — the white surcoat with a red cross of the Templars, the black cross of the Teutonic Knights — where the garment announces an institution rather than a family.
As identification it works extremely well, which is why it was adopted so quickly and so universally. A painted coat is visible at a distance, in dust and confusion, from angles where a shield is turned away.
As equipment it is a liability. A loose garment over armour catches on weapons, tangles in a press, and can be gripped by an opponent, which is one reason the long surcoat gives way to the tight jupon and eventually disappears.
And it has no protective value whatever. It is worth being blunt about this, because the surcoat is filed with armour in most collections and museum arrangement quietly implies a function it never had.
The surcoat appears in the second half of the twelfth century, and its adoption is usually connected with the crusades, where cloth over mail in a hot climate has an obvious appeal — though the identification function spread it far beyond the Latin East.
It is at its longest and loosest through the thirteenth century, the period in which heraldry itself becomes systematic and hereditary, and the two developments are plainly connected.
From the mid-fourteenth century it shortens sharply into the cyclas and then the jupon, and as plate armour becomes complete and polished in the fifteenth century the covering garment disappears almost entirely — a harness good enough to display is not one you cover up.
Almost nothing survives, for the usual reason: textile decays, and a garment worn over armour was worn out rather than preserved. What is known comes overwhelmingly from effigies, brasses, seals and manuscript illumination.
The outstanding exception is the jupon of Edward the Black Prince, made about 1376 and preserved with his heraldic achievements at Canterbury Cathedral — a padded, quartered garment of velvet and silk that shows how elaborate the late form had become.
Regional differences are mostly heraldic rather than structural. The garment is much the same across Latin Europe; what varies is the system of arms displayed on it and the conventions governing who could display what.