The capture of the Alpine regions of Raetia and Noricum in 16 CE served as a springboard for the planned subjugation of the German tribes. The first offensive between 11 and 9 BCE was successful, reaching the Elbe river. One consequence of this campaign was the exile to Rome of Arminius, the son of a vanquished German chieftain. Here, Arminius learned the military techniques of his conquerors. The Romans returned to Germania under Tiberius, and between 4 and 6 CE subdued the Marcomanni and reached the Weser before being diverted, together with much of the Roman army, to quell a massive uprising in Pannonia. Three legions remained under the generalship of Varus and his trusted aides, one of whom was Arminius, now a lieutenant. In 9 CE Arminius lured Varus into a carefully planned ambush in the Teutoburg Forest, resulting in the virtual annihilation of the Roman army.