Battle of the Allia

Battle of the Allia
	Part of the Roman–Gallic wars
	; The Servian Wall; According to Titus Livius 6.32 the censors ordered its rebuilding after the sack.
Date	387 BC (probable), 390 BC (traditional)
Location	Allia river, near Rome42°01′03″N 12°31′12″E / 42.0175°N 12.52°E
Result	Gallic victory
Belligerents
Roman Republic	Gauls; • Senones; • Boii; • Insubres
Commanders and leaders
Quintus Sulpicius Longus	Brennus
Strength
c. 5,000	c. 5,000
	Location within Italy Battle of the Allia (Lazio) Battle of the Allia (Mediterranean)

The Battle of the Allia was fought c. 387 BC between the Senones – a Gallic tribe led by Brennus, who had invaded Northern Italy – and the Roman Republic.

The battle was fought at the confluence of the Tiber river and Allia brook, 11 Roman miles (16 km, 10 mi) north of Rome. The Romans were routed and subsequently Rome was sacked by the Senones.

The dies Alliensis ('Day of the Allia') was regarded as an ill-omened day in the Roman calendar, and treated as a dies religiosus on which public and ritual activity was avoided. Although later authors such as Livy present it as a lasting civic taboo, the tradition is only attested from the 1st century BC and likely reflects later reconstruction rather than continuous observance from the 4th to the 1st century AD.