Battle of Carnuntum

The Battle of Carnuntum took place in 170 A.D. during the Marcomannic Wars. In the spring of 170 A.D. swarms of German warrior bands attacked Roman provinces along the Danube River. In furtherance of this endeavor, and for mutual protection, the king of the Marcomanni, Ballomar, had formed an alliance with the Quadi tribe. Roman Emperor Marcus Aurelius with his son-in-law and chief military adviser Tiberius Claudius Pompeianus crossed the Danube River to drive back the raiders. The Romans and Germans met outside Carnuntum in Upper Pannonia, which was the headquarters for the 14th Legion. The Roman army was inexperienced and outmatched, and the ensuing battle was a disaster for the Romans. Although the legions fought hard and bravely, the were no match for the Germanic warriors. 20,000 Romans were killed. Following this victory the Germans besieged Aquileia and sacked Opitergium. Carnuntum was the worst Roman defeat in a century.

Historiography
There is only one ancient source for the battle and that is Lucian in his book Alexander which is either a polemic or a witty satire aimed at Alexander of Abonoteichus, depending on the point of view. The description of 20,000 Roman dead might have been dismissed by historians, were it not for the fact that other historical information in that work is supported by independent ancient authors and by epigraphical and numismatic evidence.

The chronology of events of the Marcomannic Wars has a number of problems, but scholars now agree that these events took place in the Spring of 170 A.D.