The Second Age is a fictional time period from J. R. R. Tolkien's universe of Middle-earth.
The Second Age began after the banishment of Morgoth into the Void by the Lords of the West led by Eönwë the Herald of Manwë.
It lasted for 3441 years, and ended with the downfall of Sauron, when he was defeated by the Last Alliance of Elves and Men following the downfall of Númenor.
This age was characterized by the rise (eventually with increased insolence) of Númenor, the rise of Sauron in Middle-earth (and the creation of the Ringwraiths), and the early wars of the Rings between Sauron and the Elves.
See also: Timeline of the Second Age.
