[4] In 110 BC, Aulus joined the staff of his older brother, the consul Spurius Postumius Albinus, as his pro-praetorian deputy (legatus pro praetore), in a military expedition against the Numidian king Jugurtha.
[5] Spurius accomplished little[6] and eventually had to return to Rome and oversee the election of next year's magistrates, leaving Aulus in charge of the Roman camp in Numidia.
[7] Problems with the elections forced Spurius to linger in Italy longer than expected, and, in early 109, despite it being winter, Aulus allowed himself to be tempted into a bold military move on his own against the town of Suthul, where Jugurtha's treasury was located.
[9] Aulus's treaty was quickly repudiated by the Roman Senate,[7] and the disaster led a tribune of the plebs to set up a commission to investigate misconduct or treasonable behavior by magistrates in the Jugurthine war.
[20] Albinus's superior, Sulla, declined to punish the murderers and address the indiscipline in the army, allegedly because he was looking forward to his candidacy for the consulship of the following year.