The first authentic history of Rome begins about 400. The city then
possessed, possibly, three hundred square miles of territory. The
number of tribes had been increased to twenty-five. Later it became
thirty-five.

In 391 a horde of Celtic barbarians crossed the Apennines into Etruria
and attacked CLUSIUM. Here a Celtic chief was slain by Roman
ambassadors, who, contrary to the sacred character of their mission,
were fighting in the ranks of the Etrurians. The Celts, in revenge,
marched upon Rome. The disastrous battle of the ALLIA, a small river
about eleven miles north of the city, was fought on July 18, 390. The
Romans were thoroughly defeated and their city lay at the mercy of the
foe. The Celts, however, delayed three days before marching upon Rome.
Thus the people had time to prepare the Capitol for a siege, which
lasted seven months, when by a large sum of money the barbarians were
induced to withdraw.

During this siege the records of the city's history were destroyed,
and we have no trustworthy data for events that happened previous to
390.

The city was quickly rebuilt and soon recovered from the blow. In 387
the lost territory adjacent to the Tiber was annexed, and military colonies
were planted at Sutrium and Nepete upon the Etruscan border, and
also at Circeii and Setia. [Footnote: These military colonies, of which
the Romans subsequently planted many, were outposts established to
protect conquered territory. A band of Roman citizens was armed and
equipped, as if for military purposes. They took with them their wives