SHIELD (0. Eng. scild, cf. Du. and Ger. Schild, Dan. Skjold; the origin is doubtful, but may be referred to the root seen in " shell " or " scale "; another suggestion connects it with Icel. skjalla, to clash, rattle; it is not connected with the Indo-Ger. root skeu, seen in Gr. OWTOS, KVTOS Lat. culis, skin, scutum, shield, O. Eng. hyd, hide, and in " sky "), a piece of defensive armour borne upon the left arm or carried in the left hand as a protection against missiles. Varying in shape and form, it was the principal piece of defensive armour from the Bronze and Iron Age to the introduction of fire-arms, and is still borne by savage warriors throughout the world (see ARMS AND ARMOUR, and for the heraldic shield HERALDRY).
In modern times the principle of the shield has been applied to guns of all calibres from n and 10 in. calibre downwards. Whereas the turret, barbette, cupola and other heavy-armoured structures are intended to be proof against the heaviest projectiles, the shield is usually only designed to resist rifle and shrapnel bullets or very light shells. For the application of shields to field artillery, etc., see the articles ARTILLERY and ORDNANCE.