The spolia opima ("rich spoils") were the armor, arms and other effects that an ancient Roman general stripped from the body of an opposing commander slain in single combat. The spolia opima were regarded as the most honourable of the several kinds of war trophies a commander could obtain, including enemy military standards and the peaks of warships.
For the majority of the city's existence, the Romans recognized only three instances when spolia opima were taken. The precedent was set in Rome's legendary history, when in 752 BC Romulus defeated and stripped Acro, king of the Caeninenses, following the Rape of the Sabine Women. In the second instance, Aulus Cornelius Cossus obtained the spolia opima from Lar Tolumnius, king of the Veientes, during Rome's semi-legendary Regal period. The third and most historically grounded occurred before the Second Punic War when Marcus Claudius Marcellus (consul 222 BC) stripped the Celtic warrior Viridomarus, a king of the Gaesatae. The next instance recorded alleges that Augustus' adopted son Nero Claudius Drusus engaged multiple Germanic (at least three) chieftains during his conquest of Germany and defeated them in "dazzling displays of single combat" (12 BCE-9 BCE). 
The ceremony of the spolia opima was a ritual of state religion that was supposed to emulate the archaic ceremonies carried out by the founder Romulus. The victor affixed the stripped armor to the trunk of an oak tree, carried it himself in a procession to the Capitoline, and dedicated it at the Temple of Jupiter Feretrius.
During the earliest years in the rise of Augustus (still known as Octavian at the time), Marcus Licinius Crassus (consul 30 BC) defeated an enemy leader in single combat in Macedonia and was eligible to claim the honour of spolia opima. This Marcus Crassus was the grandson of the triumvir Marcus Crassus, who had died in the disastrous Battle of Carrhae in 53 BC. His illustrious political lineage made him a potential rival to Octavian, who blocked the honors. Crassus may also have been the last Roman outside the imperial family to be awarded the honor of a triumph.
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- Livy, Ab urbe condita, 1:10
- J.W. Rich, "Drusus and the Spolia Opima," Classical Quarterly 49.2 (1999), p. 545.
- Lindsay Powell , "Eager for Glory," biography p. 94-95.
- Rich, "Drusus and the Spolia Opima," p. 545.
- Ronald Syme, The Roman Revolution, p. 308
- Ronald Syme, The Augustan Aristocracy ( (Oxford University Press, 1989), pp. 273–274. The sources are not entirely clear as to whether Crassus was actually allowed to celebrate his triumph, virtually the only honor his grandfather never gained.