Who are these guys? Is Morgan a first or last name? If it's Morgan's Vigil, how come she was never seen there? Where did she raise this Militia of hers?
On the surface, Morgan's Militia seems fairly straightforward. They've been in the Burning Steppes for years now. Those of us who played Alliance back in classic can remember them and their camp at Morgan's Vigil, where they could gather various quests to penetrate Blackrock Depths and Blackrock Mountain. When Cataclysm revamped the old world, we finally were introduced to Morgan herself. Morgan's purpose in invading Blackrock Depths is to start the process of reclaiming the Steppes, formerly the Redridge Mountains before the destruction caused by the summoning of Ragnaros to Azeroth.
Morgan tells those she's willing to work with (Alliance players) that she is a survivor of the creation of the Steppes and that she intends to wage war against the Dark Irons and Ragnaros until she finally has defeated them utterly and can turn her attention toward building a new kingdom in the Steppes, one dedicated to justice and peace. As she herself says, she's there to fight for what's rightfully hers.
The only problem is, what exactly is that? What's going on with Morgan's Militia? What right do they have to start their own kingdom in the Burning Steppes, especially while flying Stormwind's colors and seeking assistance from the Alliance in general? And it's not like they're hiding that they plan to build an entirely new nation right in the middle of the Redridge Mountains, either. They're quite up front about it.