Dustwallow Marsh is a vast and ancient swamp that is home to many old and wonderful beasts. Navigation is often extremely difficult, and many adventurers have lost their way in this great jungle, where trees obscure the sunlight and raptors, spiders and crocolisks lay in wait, hunting those brave enough to venture close to their lairs.
Perhaps it is because of extreme terrain conditions that neither the Horde nor the Alliance has succeeded in establishing extensive presence in the area. Located on the tip of the peninsula on the western shore, the citadel of Theramore Isle is the home of Jaina Proudmoore and a great bastion of the Alliance. The gleaming walls of this bastion, however, often serve to contain the Alliance, and its presence does not extend far beyond them, despite a number of scattered checkpoints that dot the road leading to The Barrens. Theramore Isle military has recently been dwindling, partly due to the ever-increasing number of desertions, although why so many people have chosen to forsake their place with the Theramore garrison remains a mystery.
Despite bordering on a Horde-controlled territory, Tauren and Orc presence in Dustwallow Marsh is equally marginal and is largely confined to the Brackenwall Village to the northwest. Founded by the Stonemaul ogres and ruled by the iron fist of their leader Mor'Morokk, Brackenwall Village is the only vestige of the Horde in the area. As the Stonemaul ogres do not generally seem to take much interest in the outside world, much of the area between the bastion of Theramore Isle and the Horde settlement remains wild and untamed, with even the road leading to the Barrens rapidly falling into disrepair.
Despite the fact that neither faction controls a significant portion of the Dustwallow Marsh, covert skirmishes between the Alliance and the Horde have become common, in spite of the official truce that is maintained in the region. There have been reports of Brackenwall Village taking military action against the covert Theramore infiltrators, who have been spotted to the east of the village. Other sources indicate that a number of Horde spies have been murdered or simply disappeared while attempting to infiltrate Theramore. Clandestine activities on both sides continue to this day and are more likely to escalate into a full-fledged covert conflict than cease completely. It can be argued, in fact, that the covert war that now rages in the Dustwallow Marsh is a clear indicator of the limits of Thrall's power, as assassinations and murders continue despite his order to leave the people of Theramore Isle alone.
In the south of the marsh, the Black Dragonflight has established a presence. Consequently, these regions of the swamp have come to be known as the Dragonmurk and the Wyrmbog. Until recently, the Stonemaul ogres lived in Stonemaul Village in this region in relative peace. The Mok'Nathal, Rexxar assumed leadership of their tribe some time ago and forging an alliance between the Stonemaul and the Horde. Since that time, the Black Dragonspawn attacked the village in a terrible rout and the surviving Stonemaul ogres were forced to retreat to Brackenwall. They have sworn revenge on the usurpers. It is said that this wilderness is also home to Onyxia, a great dragon and the daughter of Deathwing, although few adventurers have ever ventured into her lair and lived to tell the tale.
Dustwallow Marsh had long been the home only to wild beasts, but all this changed in the third war, when Jaina Proudmoore led her people here to settle down after the battle with Archimonde at Mount Hyjal. Founding the city of Theramore, Jaina's humans rapidly extended into the swamp, building fortified guard towers at important points along the road to the Barrens.
The ogres of Stonemaul, having settled in the region after Thrall brought a regiment of them to Kalimdor with his fleet, were called to war upon the humans by their newly established leader Rexxar, and Dustwallow Marsh saw a great skirmish between the opposing forces, leading to the death of Admiral Proudmoore and the permanent breakup of the tentative peace between the Alliance and the Horde.
Taken from: http://www.wowwiki.com/Dustwallow_Marsh