[1] In 153 BC, Quintus Fulvius Nobilior was in charge of a 30.000 strong army to campaign in Spain, which was largely unsuccessful.
[2] The Roman army was initially deployed against the oppidum of Segeda, whose Celtiberian inhabitants, the Belli, had been expanding its walls and attacking other nearby tribes.
[2] Moving west to the meseta, Nobilior laid siege to Numantia, an oppidum whose inhabitants were to give Rome trouble for years[4] and had sheltered the Belli when they fled their city.
[6] Nobilior was designated consul in 154 BC, however his appointment could not come into effect until the Ides of March, the day for settling debts that marked the end of the calendar year.
To overcome this obstacle, and recognizing the need for immediate action, the Roman Senate decreed January 1 as the new beginning to the civil year.