Gnaeus Calpurnius Piso (consul 23 BC)
In mid-term Augustus fell ill and was expected to die, which would, in theory, have left Piso as the highest authority in the state.
[3] Piso's homonymous father was alleged to have participated in Lucius Sergius Catilina's supposed First Catilinarian conspiracy to depose the consuls elected for 65 BC.
Dispatched to Spain in 64 BC as quaestor pro praetore, on the motion of Marcus Licinius Crassus and carried likely due to a shortage of commanders, he was killed there by Pompeian assassins.
The prosecution was in retaliation for the lex Manilia, which gave Pompey command of the Roman armies in the east during the war against Mithridates.
Manilius was initially defended by Cicero, but he dropped the case after the trial was violently disrupted by a paid mob.
In 50, the Senate, led by Pompey, ordered Caesar to disband his army and return to Rome because his term as a governor had ended.
[8][1] Taking advantage of Pompey's absence from the Italian mainland, Caesar made an astonishingly fast 27-day, west-bound forced march to Hispania and destroyed the Pompeian army in the Battle of Ilerda.
Piso's light cavalry effectively disrupted these efforts, notably at the Battle of Ruspina when he harassed Caesar's defeated army as it retreated to its camp.
After Caesar's assassination in 44 BC, he joined with the tyrannicides, Marcus Junius Brutus and Gaius Cassius Longinus, during their civil war.
He was again pardoned and returned to Rome, where he refused to participate in the political arena which was under the control of Caesar's heir, Octavian (later known as Augustus).
[12] With the death of the consul-elect, Aulus Terentius Varro Murena, before he could assume office, Augustus offered the consulship to the noted republican and imperial opponent Piso.
Many explanations have been offered, including a sense of public duty, resurgence of his political ambitions, a desire to resurrect his family's dignitas after a long period of obscurity, or hope of consulships for his two sons.
