The sagum was a garment of note generally worn by members of the Roman military

Military of ancient Rome

The Roman military was intertwined with the Roman state much more closely than in a modern European nation. Josephus describes the Roman people being as if they were "born ready armed." and the Romans were for long periods prepared to engage in almost continuous warfare, absorbing massive losses...

 during both the Republic

Roman Republic

The Roman Republic was the period of the ancient Roman civilization where the government operated as a republic. It began with the overthrow of the Roman monarchy, traditionally dated around 508 BC, and its replacement by a government headed by two consuls, elected annually by the citizens and...

 and early Empire

Roman Empire

The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

. Regarded symbolically as a garment of war by the same tradition which embraced the toga

Toga

The toga, a distinctive garment of Ancient Rome, was a cloth of perhaps 20 ft in length which was wrapped around the body and was generally worn over a tunic. The toga was made of wool, and the tunic under it often was made of linen. After the 2nd century BC, the toga was a garment worn...

 as a garment of peace, it was slightly more practical in any event, consisting of a simple rectangular segment of cloth fastened by a leather or perhaps metal clasp and worn on top of the armor. The fabric was made of unwashed wool, saturated with lanolin

Lanolin

Lanolin , also called Adeps Lanae, wool wax or wool grease, is a yellow waxy substance secreted by the sebaceous glands of wool-bearing animals. Most lanolin used by humans comes from domestic sheep...

(which made it water-resistant); it was traditionally dyed bright red.