What was the War of the Ancients in World of Warcraft

The war of the ancients was considered to be the first major war on Azeroth involving the sentient races. It was a war against the burning legion when Queen Azshara and her high elves opened a portal to let Sargeras come through. Malfurion Stormrage helped to close the portal before Sargeras came through, even though he lost his daughter in the process. The blue dragonflight was also decimated during that war, due to the actions of Deathwing and his demon soul. It was then that the Sundering occurred, breaking apart Azeroth and leaving a swirling magic vortex in the center where the well of eternity used to be. This led to the creation of Nordrasill and the night elves immortality and eventually to the creation of Teldrasill.