“In the wake of the Sunwell’s purification, a period of suspicious silence swept over the world. As if on cue, the undead Scourge launched a massive assault against the cities and towns of Azeroth, this time extending its reach far beyond the Eastern Kingdoms. Under pressure to respond with a full army, Warchief Thrall deployed an expedition force to Northrend led by Overlord Garrosh Hellscream. Meanwhile, the missing human king Varian Wrynn at last returned to Stormwind City and reclaimed his crown. He sent an equally powerful Alliance army, commanded by Bolvar Fordragon, to defeat the Lich King—and any Horde forces who would stand in their way.

World of Warcraft: Wrath of the Lich King was announced on August 3, 2007, on the first day of BlizzCon 2007. Several enhancements to World of Warcraft‘s graphics engine were added with the release of Wrath of the Lich King. ”

- Source: Wikipedia