- This article is about the handheld defensive device. For other meanings of the word see shield (disambiguation)
The oldest form of shield was a protection used to block attacks by hand weapons and arrows. Shields have varied greatly in construction over time and place. Lightly armoured warriors relying on speed and surprise would generally carry small round shields sometimes made of metal but more often of wood.
The heavily armoured Roman legionaries carried large rectangular shields that could provide far more protection, but made swift movement more difficult. Famously the Romans used their shields to create tortoise like formations in which the entire group of fighters would be eclosed in an armoured box.
Shields were used in war up until the 17th century, when gunpowder powered weapons made shields obsolete in the battlefield.
Many non martial devices also employ shields. Space craft have heat shields to ensure and safe reentry. Electronics uses shielding to reduce electrical noise and crosstalk between signals. People and systems that must work in the presence of ionizing radiation are protected with shielding.
Science fiction writers have imagined many futuristic shields, usually using force fields. These include personal shields, as in the Dune series, or larger ones for spacecraft as in Star Trek. See shield (science fiction) for more.