Caesar's wars helped establish the term Germania. The initial purpose of the Roman campaigns was to protect Transalpine Gaul by controlling the area between the Rhine and the Elbe. In AD 9 a revolt of their Germanic subjects headed by the supposed Roman ally, Arminius, (along with his decisive defeat of Publius Quinctilius Varus and the destruction of 3 Roman legions in the surprise attack on the Romans at the Battle of the Teutoburg Forest) ended in the withdrawal of the Roman frontier to the Rhine. At the end of the 1st century two provinces west of the Rhine called Germania inferior and Germania superior were established. Important medieval cities like Aachen, Cologne, Trier, Mainz, Worms and Speyer were part of these Roman provinces.