War of Wrath
During the wars of Beleriand, Gothmog (the Lord of Balrogs) had a bodyguard of trolls. During the Nírnaeth Arnoediad, the Battle of Unnumbered Tears, in which Morgoth defeated the united armies of Elves, Men, and Dwarves, the great human warrior Húrin faced Gothmog's trolls to protect the retreat of the Elven king Turgon. Morgoth's order to Gothmog to capture Húrin alive allowed Húrin to kill all the trolls. Many trolls died in the War of Wrath, but some survived and joined Sauron, the greatest surviving servant of Morgoth.