28 de Janeiro de 1921.

A symbolic Tomb of the Unknown Soldier is installed beneath the Arc de Triomphe in Paris to honour the unknown dead of World War I. In many wars, huge numbers of soldiers died without their remains being identified. In modern times the practice developed for nations to have a symbolic Tomb of the Unknown Soldier that represented the war grave of those unidentified soldiers. They usually contain the remains of a dead soldier who is unidentified (or "known but to God" as the stone is sometimes inscribed), and is thought to be impossible to ever identify. Much work goes into trying to find a certain soldier, and to verify that it is indeed one of the relevant nation's soldiers.

Perhaps the first memorial of this kind in the world is the 1849 Landsoldaten ("The Foot Soldier") monument of the First war of Schleswig in Fredericia, Denmark. Another early memorial of this kind is the 1866 memorial to the unknown dead of the American Civil War.

The current trend was started by the United Kingdom when, following World War I, it first buried an Unknown Warrior on behalf of all British Empire Forces in Westminster Abbey in 1920, leading other nations to follow their example. The most famous tomb is that in France under the Arc de Triomphe that was installed in 1921 honouring the unknown dead of the First World War.

These tombs are also used to commemorate the unidentified fallen of later wars. Although monuments have been built as recently as 1982 in the case of Iraq, it is unlikely that any further ones will be constructed. Advances in DNA technology mean that even the tiniest fragment of bone is usually identifiable.

Wikipedia