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.
Imperial Roman army
Under Augustus, the European borders of the empire he inherited from his grand-uncle Julius Caesar were considerably expanded. During the first half of his sole rule (30–9 BC), Augustus' central strategic objective was to advance the Roman border from Illyricum and Macedonia to the line of the Danube, Europe's greatest river, in order both to increase strategic depth between the border and Italy and to provide a major fluvial supply route for the Roman armies in the region. The strategy was successfully executed: Moesia (29-7 BC), Noricum (16 BC), Raetia (15 BC) and Pannonia (12-9 BC) were annexed in steady succession. After settling the Danube border, Augustus turned his attention to the North, where Julius Caesar had in 51 BC established the border of Roman Gaul along the river Rhine, the second major European fluvial route. Augustus launched an ambitious strategy of advancing the Rhine border to the river Elbe, aiming to incorporate all the warlike Germanic tribes. This would eliminate their chronic threat to Gaul, increase strategic depth between free Germans and Gaul, and make the western Germans' formidable manpower available to the Roman army. But a massive and sustained military effort (6 BC – AD 9) came to nothing. Roman advances in Germania Magna (i.e. Germany outside the empire) had to be scaled down during the Great Illyrian Revolt of AD 6-9, when many troops were diverted to Illyricum. Then Augustus' expansion strategy suffered a crushing setback when some 20,000 Roman troops were ambushed and massacred by the Germans at the Battle of the Teutoburg Forest in AD 9. After this, Augustus shelved his Elbe strategy. It was apparently revived briefly by his successor Tiberius, whose nephews, the generals Germanicus and Drusus, launched major and successful operations in Germania in AD 14-17, during which the main tribes responsible for Varus' defeat were crushed and the three lost legionary "aquilae" (eagle-standards) were recovered.