<P> "Dog tag" is an informal but common term for the type of identification tag worn by military personnel . The tags are primarily used for the identification of dead and wounded soldiers; they have personal information about the soldiers and convey essential basic medical information, such as blood type and history of inoculations . The tags often indicate religious preference as well . Dog tags are usually fabricated from a corrosion - resistant metal . They commonly contain two copies of the information, either in the form of a single tag that can be broken in half or two identical tags on the same chain . This duplication allows one tag (or half - tag) to be collected from a soldier's body for notification and the second to remain with the corpse when battle conditions prevent it from being immediately recovered . The term "dog tags" arose because of their resemblance to animal registration tags . </P> <P> The earliest mention of an identification tag for soldiers comes in Polyaenus (Stratagems 1.17) where the Spartans wrote their names on sticks tied to their left wrists . A type of dog tag ("signaculum"), was given to the Roman legionnaire at the moment of enrollment . The legionnaire "signaculum" was a lead disk with a leather string, worn around the neck, with the name of the recruit and the indication of the legion of which the recruit was part . This procedure, together with enrolment in the list of recruits, was made at the beginning of a four - month probatory period ("probatio"). The recruit got the military status only after the oath of allegiance ("sacramentum"), at the end of "probatio", meaning that from a legal point of view the "signaculum" was given to a subject who was no longer a civilian, but not yet in the military . </P> <P> In more recent times, dog tags were provided to Chinese soldiers as early as the mid-19th century . During the Taiping revolt (1851--66), both the Imperialists (i.e., the Chinese Imperial Army regular servicemen) and those Taiping rebels wearing a uniform wore a wooden dog tag at the belt, bearing the soldier's name, age, birthplace, unit, and date of enlistment . </P>

When did the military start using dog tags
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