Top Roman Military Defeats

Which were Ancient Rome's worst military defeats? Were they those that from our perspective changed history or the ones that the Romans held up as cautionary tales -- the ones that made them stronger? Here are the worst defeats in battle suffered by the ancient Romans.

These defeats are listed chronologically from the more legendary past to the better-documented defeats during the Roman Empire.


[Celts defeat the Romans.] "The Allia, c. 387 BC: A hastily assembled citizen army led by military tribunes is defeated by the Gallic Senones just 11 miles north of Rome. Not only is the army scattered with heavy losses, but the city is subsequently devastated by the victorious Celts, thus casting a shadow over Romano-Gallic relations for the next 400 years." -KL47 "Because of the ​centuries-long effect it had on the Roman psyche." -cjriga More »

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Caudine Forks

Battle of the Caudine Forks
Public Domain. Courtesy of Wikipedia.

[Samnites humiliate the Romans.] "The Caudine Forks, 321 B.C.: The consuls T. Veturius Calvinus and Sp. Postumius obligingly march their army into a trap laid by the Samnites and are forced to surrender and 'pass under the yoke'. A relatively bloodless affair, but by far the most humiliating event in the entire history of the Republic. Definitely Rome's Spinal Tap moment." -KL47

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Battle of Cannae (Punic War II)

Destruction of the Roman Army at the Battle of Cannae
Public Domain. Courtesy of Wikipedia.

[Costly Punic War defeat.] "Cannae, 216 BC: Consuls C. Terentius Varro and L. Aemilius Paullus are defeated by Hannibal's numerically inferior army.... Polybius claims 70,000 dead and 10,000 captured, though Livy, Appian and Plutarch report "only" 50,000 dead." -

In raw numbers, this has to be the worst military defeat Rome ever suffered. In addition, it forced Rome to completely rethink every aspect of it's military.... Without Cannae, there would never have been the Legions of the Empire." -cjriga

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Public Domain. Courtesy of Wikipedia
[Squabbling, snobbery between Romans led to the destruction of both their armies.] "Arausio, 105 BC: The armies of consul Cn. Mallius Maximus and proconsul Q. Servilius Caepio are defeated by the Cimbri and Teutones on the Rhône. Some sources report even higher casualties than at Cannae: Livy cites the claim by the annalist Valerius Antias that 80,000 soldiers and 40,000 servants and camp followers were killed, though this is probably an exaggeration. The most important result is the rise to power of C. Marius and his reform of the legions into a professional army." -KL47 More »
Silver denarius from 19 B.C. Shows Liber and a Parthian kneeling.
Bust of Liber; R TVRPILIANVS III VIR Parthian kneeling right, presenting standard with X. © CNG Coins

[Destroyed the fragile balance of Roman power.]"Battle of Carrhae (53 B.C.). With the death of Crassus, a final confrontation between Caesar and Pompey became inevitable. It wasn't the crossing of the Rubicon that was the death knell of the Republic, but the death of Crassus at Carrhae." -cjriga

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The Teutoburg Forest

Burial slab for a Roman soldier who died at Teutoberg Wald.
Irene Hahn

[Germans treacherously ambush Romans.] "Teutoburg Forest, AD 9: Three legions under P. Quinctilius Varus, governor of Germania, and their civilian hangers-on are ambushed and virtually wiped out by the supposedly friendly Cherusci led by Arminius. Total Roman losses are probably well under 20,000, but the disaster means that the frontier coalesces on the Rhine rather than the Elbe as planned." -KL47 "This defeat marked the end of any hope of expansion across the Rhine. More than that, it marked a change in Imperial policy." -cjriga

Map of the Battle of Adrianople
Public Domain. Courtesy of Wikipedia

[Goths shouldn't have, but did defeat an emperor.] Adrianople (Hadrianopolis) This is my pick, although Teutoberg would be my strong second choice. On August 9, A.D. 378, Valens was killed and his army lost to an army of Goths led by Fritigern, whom Valens had given permission only two years earlier to settle in Roman territory. Two-thirds of the Eastern army were killed. Ammianus Marcellinus called it "the beginning of evils for the Roman empire then and thereafter." - NSG

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Alaric's Sack of Rome


[Momentous event, but mainly symbolical.] "Alaric's Sack of Rome (August 24th, 410 A.D.). What can you say? This, more than any other moment, marks the end of the Western Roman Empire." -cjriga

An attack on Rome was symbolically serious, which was why Alaric sacked the city, but Rome was no longer central politically and the sacking wasn't much of a Roman military defeat. (NSG)