As the Kingdom of Azeroth was founded by the migrant nobility of the Arathorian Empire, heavily armored warriors rose to great feats of glory and horsemanship. To give such heroes recognition amongst the people of the kingdom, the House of Wrynn established the Brotherhood of the Horse as a royal vanguard of knights. They fought for the royal family during the warring kingdoms era, and amassed great wealth for the kingdom as they led the royal army to expand the nation's borders.
To honor their dedication and service to the crown, the royal family funded the construction of the tower of the Brotherhood. The order's bastion of power and its surrounding buildings sometimes show their influence, such as horse heads in various ornamentation.
At the onset of the orcish wars, the Brotherhood of the Horse fought valiantly in defense of the kingdom. Outnumbered and overwhelmed, the knights manning Karazhan were slaughtered. The fallen sorcerer Medhiv took residence in the seat of Stormwind's knighted power, directing his orcish minions to ravage the landscape. Most of the knights were killed fighting in the last battles of the war, but took many orcs with them. Many of the knights who fell to the orcs were transformed into death knights by Gul'dan.
One of the most notable members of the Brotherhood was Anduin Lothar, who became a knight champion. After the First War, in recognition of his services to his people, Sir Lothar was given the title of Regent Lord of Azeroth. Rallying the people of Azeroth across the sea to Lordaeron, Lord Lothar brought about the Alliance of Lordaeron that contended with the Orcish Horde during the Second War. The remaining knights of the Brotherhood of the Horse fought alongside the armies of the Alliance of Lordaeron, offering their expertise in orcish combat.
After the Horde's mysterious retreat from Lordaeron and Grand Admiral Proudmoore's victories at sea, Lothar led the armies of the Alliance to liberate much of Azeroth and Khaz Modan (meeting up with Muradin and Brann Bronzebeard), eventually breaching the Black Morass itself. Lothar was killed at the foot of Blackrock Spire after a force of Alliance troops he personally commanded was ambushed by the Horde forces.
Anduin did not live to see his beloved homeland freed from orc control and rebuilt, but a massive stone statue depicting Lothar in his last charge was built (by orcish prisoners of the Alliance no less) and still stands in the Burning Steppes, pointing defiantly towards Blackrock Spire.
Anduin lives on in all the free warriors of the newly reivented Brotherhood of the horse. As the kingdom of Stormwind combats the dangers of the legion and multiple betrayal of horde forces the torch was relit in Lord Lothar's legacy. The membership of the brotherhood is no longer restricted to plate-wearing mounted warriors. A number of mages, rangers, and even citizens of great utility to the kingdom have been knighted as honorary members of the brotherhood.
Now more than ever the Brotherhood stands ready to deploy, engage, and destroy, the enemies of the people of Stormwind and the Alliance whereever they should muster. We are a mobile machine made up of a multiculture of warriors who will live and die for the people, blessed by the light.