Angrivarii
The wars began in the last years of the reign of Augustus, first emperor of Rome. Augustus died an old but respected man in the year 14 and was celebrated with much pomp and splendor. He left a document to be read to the senate posthumously, expressly forbidding extension of the empire beyond the Rhine. News of the will was welcomed by the Germans, thinking it gave them a free hand in the region. Germanicus found it necessary to pacify the border, which he did by a combination of scorched earth raids and offers of alliance with Rome - in short, stick and carrot. These raids also kept the army of the lower Rhine distracted from the possibility of mutiny, which had broken out on Augustus's death and only been quelled by concessions and executions.
Augustus
By 23 BC, some of the un-Republican implications were becoming apparent concerning the settlement of 27 BC. Augustus' retention of an annual consulate drew attention to his "de facto" dominance over the Roman political system, and cut in half the opportunities for others to achieve what was still nominally the preeminent position in the Roman state. Further, he was causing political problems by desiring to have his nephew Marcus Claudius Marcellus follow in his footsteps and eventually assume the Principate in his turn, alienating his three greatest supporters – Agrippa, Maecenas, and Livia. He appointed noted Republican Calpurnius Piso as co-consul in 23 BC, after his choice Aulus Terentius Varro Murena (who had fought against Julius Caesar and supported Cassius and Brutus) was executed in consequence of his involvement in the Marcus Primus affair.