Thranduil

At the end of the Second Age, the War of the Last Alliance broke out. When Oropher and Amdír/Malgalad of Lorien learned of the alliance, they came with their valiant but poorly equipped Wood Elves, even without being summoned. (...) “The Wood Elves were bold and brave, but they were poorly equipped in armor and weapons compared to the Elves of the West; they were also independent and unwilling to submit to the supreme command of Gil-galad.” Amdír died at the Battle of Dagorlad. “(...) Malgalad and more than half of his men perished in the great Battle of Dagorlad, having been separated from the main body of the army and driven back into the Dead Marshes. . .” Likely blinded by rage, and disobeying Gil-galad's orders, Oropher attacked Barad-dûr with his elite warriors, perhaps believing Sauron's forces were weaker than they actually were after Dagorlad. This mistake cost the Elven-king his life, as well as a great number of Wood Elves. "(...) Oropher died in the first assault on Mordor, advancing at the head of his bravest warriors, before Gil-galad could give the signal to attack. ..."

Thranduil took command of the remaining Silvan forces in the final assault on Barad-dûr, and subsequently ascended the throne, spending several years restoring order to his realm. It was 3434 SE, and the war was drawing to a close. “Thranduil, his son, survived, but when the war ended… he returned to his homeland with only a third of the army that had gone to war.”
Thranduil was the only son of Oropher, King of the Woodland Realm. He was born during the First Age and lived in Doriath sometime before the Second Kinslaying. [2] At the beginning of the Second Age, some Sindar traveled east and Oropher eventually founded the Elven kingdom in Great Greenwood.

In the year 3434 of the Second Age, Thranduil and his father fought in the Battle of Dagor

Thranduil is one of the Sindar, or Grey Elves, who speak Sindarin, as opposed to Quenya, the language spoken by the Noldor Elves, such as Galadriel. [1] The name "Thranduil" means "vigorous spring" in Sindarin. [T1] After the end of the First Age and the destruction of much of Beleriand during the War of Wrath, many Sindar migrated east across Middle-earth. Crossing the Misty Mountains, they encountered populations of Wood Elves living in the forests bordering the River Anduin. The Sindar were welcomed by these people, and some were appointed leaders and rulers over them. In Appendix B of The Lord of the Rings, Tolkien states that Thranduil was one of the Sindar who migrated east at the beginning of the Second Age and established kingdoms among the Wood Elves. [T 2] Later writings in Unfinished Tales make Oropher, Thranduil's father, the founder of the kingdom, which originally included the southern parts of Great Greenwood, later known as Mirkwood. [T 3]

Tolkien described Thranduil in The Hobbit as having "golden hair" and wearing a crown of leaves and red berries in autumn, and a similar crown of flowers in spring. [T 4] Thranduil marched with his father and a large army of his people to join the Last Alliance of Elves and Men in their war against Sauron at the end of the Second Age. The Elves suffered heavy losses, including Oropher, who died at the Battle of Dagorlad, outside the Black Gate of Mordor. [T 3] After the war, Thranduil, now king of his people, led the remnants of his army, only a third of what had set out, back to his home in Mirkwood. [T 5] Upon learning of the Disaster of the Gladden Fields shortly after his return, Thranduil set out to aid the Dúnedain; He arrived too late to save them, but he was able to complete the destruction of the orc horde and prevent the mutilation of the dead.