Testudo

among the ancient Romans, a defensive cover or screen formed by overlapping shields. The name comes from testa, meaning a shell, particularly a tortoise shell. When a party of Roman soldiers advanced to storm a wall or against the enemy they were wont to close up their files. Each man elevated his oblong shield or target above his head, overlapping it with that of his comrades in such a way that the shields of the company formed a roof or protection against the darts or other missiles of the enemy. Caesar relates that on one occasion the javelins of the enemy hurled through the air fell upon the testudo and pinned the edges of the shields together in such a way that it was difficult for the soldiers to pull their targets apart when they desired to engage the enemy individually. The term was applied also to a movable structure on wheels or rollers used for protecting sappers and miners as they endeavored to undermine a wall.