The Subarmalis and Thoracomachus

In the Roman army, wearing a armour was an essential part of soldier protection. Less known, however, is that protective undergarments were also worn underneath, such as the subarmalis or the thoracomachus. These padded garments played a crucial role in both the comfort and safety of Roman soldiers.

This article discusses the origin, function, composition, variants, and historical context of these undergarments, with particular attention to their role within the Roman army, archaeological findings, and application in modern reenactment practices.

The word subarmalis is composed of two Latin words: sub (under) and armus (arm or shoulder), which can be literally translated as "clothing worn under the shoulder." Although the term is not frequently found in ancient texts, sculptures and archaeological research show that this clothing was widespread in the Roman army.

The subarmalis was typically a short sleeveless or short-sleeved garment, made from leather, linen, wool, or felt. It was often padded—especially at the shoulders and chest—and sometimes featured pteryges: strip-like decorations at the hips and shoulders. By using multiple layers of material or padding, it provided protection against chafing and pressure points caused by metal armor components such as the lorica segmentata (plate armor), lorica hamata(chainmail shirt) or lorica squamata (scale armor)

Although armors such as chainmail were very effective against cuts and stabs, they offered little protection against the force of a blow. The subarmalis acted as a kind of damper, similar to a medieval gambeson. It could soften the impact of blows while simultaneously preventing detached metal parts, such as rings of a chainmail shirt, from causing wounds.

An East Roman military author from the late Roman period (possibly Justasianus) stated that the armor should not be worn directly on regular clothing, but on a special garment that was at least one finger thick. This indicates that the subarmalis had to be at least 1 to 2 cm thick – enough to provide protection and comfort.

The term thoracomachus is rare and appears in only a few sources. In that context, it is described as a padded garment made of felt and leather worn under or instead of armor. Although some researchers see it as a separate type of undergarment, it is generally believed that the thoracomachus and the subarmalis refer to the same type of garment.

Both terms indicate undergarments with a protective function, primarily aimed at the comfort of the wearer and reducing direct damage to the armour.

The subarmalis was worn by virtually all ranks within the Roman army. Ordinary soldiers, such as legionaries and auxilia, wore simple versions of linen or leather, without much decoration. Officers such as centurions or standard-bearers often had richer versions with double rows of pteryges and fringes. High officers such as legates or generals often wore the most luxurious versions, with three rows of pteryges, decorative patterns, and sometimes metal plaques.

The subarmalis was not worn exclusively during battles. Even in periods of rest — during marches, at camp stays, or during ceremonies — the subarmalis could be worn separately from the armour. This offered more comfort while still providing a certain degree of protection.

Byzantine sources indicate that armors were often stored in leather bags and hung on saddles during travels. This applied to both cavalry and infantry, but in wartime, wearing the armor was mandatory, even when danger seemed absent.

Although the subarmalis offered protection, it also had drawbacks. For instance, it reduced the ventilation of the armour. Especially in hot weather, the subarmalis was sometimes omitted to prevent overheating — not because of the weight (usually only 2 to 4 kg), but due to the limited air circulation.

Some soldiers therefore preferred to wear the armor directly on their tunic, although this was discouraged by military writers. Nevertheless, most soldiers quickly became accustomed to wearing the full gear, including the subarmalis.

Various Roman tombstones depict soldiers with a clearly visible subarmalis, sometimes with one or more rows of pteryges. The tombstone of Marcus Favonius Facilis (Legio XX Valeria Victrix, Colchester, 43–50 AD) shows a subarmalis with one row of pteryges. Another tombstone, that of Quintus Lucchius Faustus from Mainz (second half of the 1st century), shows a more elaborately executed example.

Statues of high-ranking officers, such as those found in the Julian Basilica in Corinth, also depict subarmalis clothing with multiple rows of pteryges and decorative elements.

For reenactment or film productions, subarmales are often reconstructed with leather or linen as the outer layer, and wool, cotton or synthetic padding as the inner layer. The pteryges are usually made from multiple layers of fabric and sometimes reinforced with a hem along the edges to obtain extra stiffness.

The subarmalis and thoracomachus were an indispensable, yet often overlooked component of the Roman military equipment. Their combination of comfort, protection, and decoration made them a versatile garment, forming an important bridge between man and metal.

Through their presence on tombstones, in military manuals, and via reconstruction by modern historians and re-enactors, we gain a better understanding today of the life and trials of the Roman soldier. And with that, more appreciation for the clever techniques with which the Roman army protected its people – not only with steel, but also with fabric.