Union of Maedhros
From Tolkien Gateway
The short-lived alliance of the Sons of Fëanor with the Elves of the Houses of Fingolfin and Finarfin, the Men of the Houses of Bëor, Haleth, Hador, Bór and Ulfang, and the Dwarves of Nogrod and Belegost, formed after the Dagor Bragollach and destroyed in the Nirnaeth Arnoediad.