The "Second Age" is a significant period in the fictional history of Middle-earth, created by J.R.R. Tolkien. It follows the First Age and precedes the Third Age, lasting for about 3,441 years. This era is marked by the rise and fall of powerful kingdoms, including Númenor and Gondor, and the emergence of the One Ring. During the Second Age, the Dark Lord Sauron sought to dominate Middle-earth by forging the One Ring. The age culminated in the War of the Last Alliance, where the forces of Elves and Men united to defeat Sauron, leading to a temporary peace before the events of the Third Age.