AI overview
I don't have enough context to write an accurate overview, as "9" could refer to many different things (the number 9, the year 2009, a film titled "9", etc.). Could you provide more specific context about what "9" refers to?
AI-generated from the Wikipedia summary — may contain errors.
Article
Cenotaph of a centurion who died in the Battle of the Teutoburg Forest (AD 9). Teutoburg Forest is commonly seen as one of the most important defeats in Roman history, bringing the triumphant period of expansion under Augustus to an abrupt end. The outcome of this battle dissuaded the Romans from their ambition of conquering Germania, and is thus considered one of the most important events in European history.
The 0s began on January 1, AD 1 and ended on December 31, AD 9, covering the first nine years of the Common Era.