Why were roman shields different shapes and sizes?

Answer 1

Roman shields changed in shape and size because of changes in military formation and tactics.

From the 6th century BC to the 4th century BC the Romans used the clipeus. It originated from Greece. The Greeks introduced this shield when they introduced the hoplite military formation and tactics. It was a small round shield made of bronze which was carried on the arm. It was then replaced by the parma and the scutum.

The parma was a round shield which was a 91 centimetres (36 in.) in diameter and was made of metal, making it very effective. It was used by the light infantry in the Early- and Mid- Republic.It was a Roman innovation. It was scrapped when the light infantry was also scrapped and all legionaries used the same weapons and equipment, thus getting replaced by the scutum which was previously the shield of the heavy infantry.

The scutum originated from the Samnites. It was introduced when the Romans adopted the manipular military formation and tactics of the Samnites during the Second Samnite War (326-304 BC). It was originally oval and curved and was made of two sheets or strips of bentwood glued together to make a convex curve to deflect javelins and blows. They were covered with canvas and hide and the edges were bound in rawhide or iron. Later the scutum changed in shape and became rectangular. As they were also curved, they formed a semi-cylinder. They had a round boss of bronze, brass of iron at the centre. The best surviving example has been found in Syria. It is 1.06 metre (42 in) high, a distance around the curve of 0.86 metre (34 in) which made its width, a depth of 66 centimetres (26 in) a thickness of 5-6 millimetres and weighs 10 kilos (22 pounds). The rectangular version of the scutum remained the shield of the Roman soldiers for the rest of Roman history.