Day of the Dragon
The kingdoms of humans, dwarves, elves, and other good races had been separated and fractured throughout history. Over the last 2,000 years, the younger races had come to learn of one another but remained separate and distant.
The second assault of the Orcish horde forced the kingdoms to coalesce into the Lordaeron Alliance. The horde had taken much of the continent of Khaz Modan and had cut a swath into human lands before the alliance had the opportunity to mount a reasonable counter attack.
The Alliance was distracted by an epic battle with the Aspect of the Black Dragonflight, Deathwing. Deathwing's goal was to slaughter or enslave all mortals. With the help of the best mages of the Kirin Tor, Deathwing was defeated and fell into the great sea. With Deathwing defeated, the Alliance could turn back to the threat of the Horde.
When the Horde's defeat was at hand, a plot was uncovered that would betray the Alliance into the hands of the Orcish Warchief Doomhammer. The plot was hatched by Aiden Perenolde, the king of the small human nation of Alterac. It would have allowed Doomhammer to march directly to the capital city of Lordaeron unopposed. Perenolde was found out, and the Alliance forces swiftly crushed the small kingdom.
During the lull in the fighting, Doomhammer decided to strike with sheer numbers at Lordaeron. If not for some unknown betrayal in the ranks of the Horde, it would have succeeded. Taking advantage of the weakened Horde, King Terenas of Lordaeron mounted an attack on Blackrock Mountain itself, the stronghold of the Horde. There he found a terrible truth: while the remanants of the Horde had been shattered, they had found allies in the great red dragonflight. Doomhammer was defeated with massive Alliance losses. He was captured, along with a large portion of the Horde. The fortresses of Grim Batol remain impenetrable, but without a leader the Horde is aimless, ravaging towns nearby where they can. The leader of the mages (the Kirin Tor), Antonidas, took a small contingent of the most powerful heroes of the Alliance and destroyed the Dark Portal from which the Orcs invaded.
With the destruction of the Dark Portal The Second War effectively ended. And thus, the glue that held together the struggling Alliance began to dry and crack. King Terenas Menethil II still holds ultimate rule over the alliance, but each of its contingents stands ready to withdraw, leaving the Alliance defenseless should the Orcs return, or worse, should the Burning Legion strike Azeroth again. An army of the Alliance, led by Uther Lightbringer, head Paladin of the Silver Hand, is readying north of Khaz Modan to strike at the remnants of the Horde. The mystery remains as to how the Horde commands the red dragonflight, and how the Alliance must deal with Lord Perenolde's betrayal and the shattered kingdom of Alterac.