The Scutum (English pronunciation: /ˈskuːtəm/; plural scuta; Classical Latin: [ˈskuːtũː]) was a type of shield which was in use among Italic peoples in the archaic period. It was adopted by the army of ancient Rome. This was probably in the fourth century BC. The Romans adopted it when they switched from the military formation of the hoplite phalanx of the Greeks to the formation with maniples. In the former, the soldiers carried a small round shield, which the Romans called clipeus. In the latter, they used the scutum, which was a larger shield. Originally it was an oblong and convex shield. By the first century BC it had developed into the rectangular, semi-cylindrical shield we, in modern times, associate the scutum with. This was not the only shield the Romans used. Roman shields were of varying types depending on the role of the soldier who carried it. Oval, circular and rectangular shields were used throughout Roman history.
In the early days of Ancient Rome (from the late regal period to the first part of the early republican period,) Roman soldiers wore clipeus, which was like the aspides (ἀσπίδες), a small round shield used in the Greek hoplite phalanx. The hoplites were heavy infantrymen who originally wore a bronze shield and helmet. The phalanx was a compact, rectangular mass military formation. The soldiers lined up in very tight ranks in a formation which was eight lines deep. The phalanx advanced in unison, which encouraged cohesion among the troops. It formed a shield wall and a mass of spears pointing towards the enemy. It compactness provided a thrusting force which had a great impact on the enemy and makes frontal assaults against it very difficult. However, it also had its drawbacks. It worked only if the soldiers kept the formation tight and had the discipline needed to keep its compactness in the thick of the battle. It was a rigid form of fighting and it maneuverability was limited. The shields being small provided less protection. However, their smaller size afforded more mobility. Their round shape enabled the soldiers to interlock them to hold the line together.