In ancient Roman warfare, the testudo or tortoise formation was a type of shield wall formation commonly used by the Roman legions during battles, particularly sieges.
Roman soldiers in "tortoise" formation
The testudo formation in a Roman military reenactment
17th century depiction by Wenceslaus Hollar
2005 Belize unrest
A shield wall is a military formation that was common in ancient and medieval warfare. There were many slight variations of this formation,
but the common factor was soldiers standing shoulder to shoulder and holding their shields so that they would abut or overlap. Each soldier thus benefited from the protection of the shields of his neighbors and his own.
Anglo-Saxon shield wall against Norman cavalry at the Battle of Hastings (scene from the Bayeux Tapestry).
Ancient depiction of Sumerian infantry shield wall, from the Stele of the Vultures honoring the victory of king Eannatum of Lagash over Umma, c. 2500 BC
Roman legionaries in formation, Stele found at Glanum, on display at the Gallo-Roman Museum of Lyon-Fourvière
Police form a testudo shield wall