Which battle ends the First Age in J.R.R. Tolkien’s history of Middle-earth?

The War of Wrath ends the First Age in J.R.R. Tolkien’s history of Middle-earth.

The War of Wrath is the final conflict of the First Age, fought between the forces of the Valar and the armies of Morgoth. It brings the long wars over the Silmarils and the fate of Beleriand to a catastrophic conclusion. Morgoth is defeated, captured, and cast out of the world.

The conflict is described in The Silmarillion and associated texts rather than narrated as a full conventional battle novel. Its destruction reshapes the geography of the world: much of Beleriand is drowned beneath the sea. The surviving Elves and Men then enter a new historical era.

The War of Wrath is easy to confuse with later battles. The Battle of Dagorlad and the Last Alliance belong to the Second Age, while the Battle of Five Armies occurs near the end of the Third Age. The War of Wrath is specifically the First Age’s climactic war.