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.
History of Rome
The years 44–31 BC mark the struggle for power between Marcus Antonius and Octavian (later known as Augustus). Finally, on 2 September 31 BC, in the Greek promontory of Actium, the final battle took place in the sea. Octavian was victorious, and became the sole ruler of Rome (and its empire). That date marks the end of the Republic and the beginning of the Principate.