At the dawn of human civilization, the human race was split up into tribes. These tribes were eventually united by the Arathi tribe into one great nation known as Arathor. The capital of this nation was Stromgarde, a fortress in the Arathi Highlands. Eventually, Arathor splintered into the seven kingdoms that formed the first Alliance of Lordaeron -- Dalaran, Gilneas, Arathor -- now called Stromgarde, Stormwind, Kul Tiras, Alterac, and Lordaeron.
During the Third War, Stromgarde fell -- and its leader, Thoras Trollbane, was assassinated. His son Galen became the leader of Stromgarde, but he was killed by Horde some time between the events of Wrath
-- he's now an undead quest giver who seems to have given up all hope of reclaiming his land, and instead works for Sylvanas. In the meantime, the remaining survivors of Stromgarde still fight from Refuge Pointe to try and reclaim the last bastion of what was once a mighty empire.
Except that Galen wasn't the only Trollbane. Galen's cousin Danath was a lord of Stromgarde at one point in time, until he left with the Alliance Expedition to Draenor after the Second War. Since then, Danath has been fulfilling his duties in Outland, although he's vowed that one day, he'll return to Stromgarde and restore it to greatness. Stromgarde isn't just a ruined city -- it represents the history of human civilization itself.
And it also represents a foothold in the north. While we don't know for certain what Stromgarde is going to involve, there are several possibilities. This could be the next leg of Varian's trials of the High King. It could be Danath's return to Stromgarde. It could be a battle between the Forsaken and the soldiers of Refuge Pointe. What it makes me wonder, however, is how it will end. Will we just have a scenario, or does this scenario hold the potential for a new in-game Alliance base near Hillsbrad, replacing the devastating loss of Southshore? Only time, and the new PTR, will tell.