A tropaion, whence English "trophy" is derived, is an ancient Greek and later Roman monument set up to commemorate a victory over one's foes. Typically this takes the shape of a tree, sometimes with a pair of arm-like branches upon which is hung the armour of a defeated and dead foe. The tropaion is then dedicated to a god in thanksgiving for the victory.
Greece
In the Greek city-states of the Archaic period, the tropaion would be set up on the battlefield itself, usually at the site of the "turning point" at which the routed enemy's phalanxbroke, turned and ran. It would be dressed in the typical hoplite of the period, including, a helmet, cuirass, and a number of shields, etc., would be piled about the base. It remained on the battlefield until the following season's campaigns, where it might be replaced with a new trophy. In later eras in the Greek world, these tropaia might be vowed at the battle-site, but in fact erected at pan-Hellenic sanctuaries such as Olympia or Delphi to further increase the prestige of the victorious state. The significance of the monument is a ritualistic notification of "victory" to the defeated enemies. Since warfare in the Greek world was largely a ritualistic affair in the archaic hoplite-age, the monument is used to reinforce the symbolic capital of the victory in the Greek community. Another interpretation of the tropaion is that it was a monument dedicated to the slaughter of the enemy. Key passages describe that the tropaion was the last stage of battle, following the critical rout and chase of the enemy. A critical passage of Thucydides suggest that the tropaion was set up to celebrate the enemy killed in battle. Ancient sources attest to the great deal of significance that early Greek cities placed upon symbols and ritual as linked to warfare – the story involving the bones of Orestes, for example, in Herodotus 1 which go beyond the ritualistic properties to even magically 'guaranteeing' the Spartan victory, displays the same sort of interest in objects and symbols of power as they relate to military success or failure.
Rome
The tropaeum in Rome, on the other hand, would probably not be set up on the battle-site itself, but rather displayed prominently in the city of Rome. Romans were less concerned about impressing foreign powers or military rivals than they were in using military success to further their own political careers inside the city, especially during the later years of the Republic. A tropaeum displayed on the battlefield does not win votes, but one brought back and displayed as part of a triumph can impress the citizens or the nobles. The symbolism of the tropaeum became so well known that in later eras, Romans began to simply display images of them upon sculpted reliefs, to leave a permanent trace of the victory in question rather than the temporary monument of the tropaeum itself.
