Battle of the Teutoburg Forest
His rivalry with Arminius, the Cheruscan leader who inflicted the devastating defeat at the Battle of the Teutoburg Forest on the Romans under Publius Quinctilius Varus in 9 AD, prevented a concerted attack on Roman territory across the Rhine in the north (by Arminius) and in the Danube basin in the south (by Maroboduus).