Octavian defeated Mark Antony at Actium in 31 BC and became supreme ruler of the Roman world. Four years after this victory he reached a constitutional settlement with the Senate of Rome which gave him the title "Augustus" and made him the first Roman Emperor. Under this agreement the provinces were categorized into two groups, the peaceful, which were left in control of senatorial governors and the other provinces which were deemed rebellious remained in control by military forces. Augustus delegated nominees to various governorships although he still kept Egypt under his own personal supervision.
Augustus' foreign wars were fought in order to strengthen the frontiers. He stretched the northern border all the way to the Danube and in the process overtaking the Alps and Balkans. However, the most serious setback was caused by the hands of the Balkans and the Germans. Augustus' stepson Drusus fought a series of successful battles between 12 and 9 BC and by 6 AD, the Roman armies (under Drusus' brother Tiberius) were poised to invade Marcomanni and complete their conquest of central Europe. But before this could be done, a rebellion in the Balkans forced the plan to be shelved. Three years later in 9 AD, the German armies ambushed three Roman legions in the Teutoburg forest and massacred them. The Roman frontier was pulled back from the hoped to be new border of the River Elbe to the former frontier, the Rhine.