But why would they?
I mean lets suppose Arthas is persuaded not to cull Stratholme, that is what is called in such genre the ‘Point of Divergence’ as in where the thing that did happen, doesn’t happen. So. How does this leave the world at that point? Well, some of it will look good, some of it not so good, some of it terrible.
Initially, on Eastern Kingdoms, life would be good, between the surviving human Kingdoms of the East (Apart from Gilneas and Strom, who had already left), and Quel’thalas (who had left the Alliance, but were a friendly neutral nation, plus Gnomes and Goblins, the Scourge such as it was, would have died in its infancy, there would be no Arthas to weld it together into the terrifying instrument of death it became. Could someone else have been chosen as Lich King? yes. Would it have had the same shattering impact on Morale as the Crown Prince of Lordaeron doing so? No.
So lets assume that the Eastern Kingdoms fights a bloody, but ultimately victorious war against the proto Scourge. This will take some time. The Good news is that Quel’thalas is not invaded, Othmar Garithos is just a bitter old racist provincial petty noble with no power, and better minds in Lordaeron command the Alliance (Quite possibly Arthas himself) Therefore no racism to drive a wedge between the Elves and Lordaeron, No invasion means 90% of them didn’t die on a non existant Dead Scar. This means no blood to be honoured in the name of the fallen. As such, the High Elves do not rename themselves Blood Elves, they all remain High Elves under King Anasterian and Crown Prince Kael’thas, Ranger General Sylvanas Windrunner and Ranger Lord Lor’themar Theron. They are Neutral to the Alliance, but generally have their back.
However. In Kalimdor…
The fleeing Orcs make contact with the Darkspear, history rocks on as it did, they then make contact with the Tauren. No changes there.
The Alliance is not in fit state yet to go charging across the Ocean to Kalimdor and build Theramore. Apart from anything else, Jaina actually has a reason to -stay- in the Eastern Kingdoms, as her beloved is no longer a rampaging Zombie King in this timeline.
As such the Proto Horde has some breathing space. Which is good. They’ll need it. The Forsaken would not exist as a species, because the situation behind their creation was unique to Arthas and Sylvanas and their clash. Both are happily alive, and the Scourge eradicated, so no Forsaken.
The Horde have Zero presence, really, on the Eastern Kingdoms, apart from scattered bands, and perhaps the Frostwolves, who would almost certainly be forced to sue for peace. Given that the only ones of the Alliance who wanted them put to death were Strom, Gilneas and Quel’thalas, none of whom are in the Alliance anymore. Even if Jaina -does- harbour any desires to create a working Peace with the Orcs, it is likely to be with these Frostwolves, very probably with Drek’thar.
So then we have a situation where the Alliance de facto controls the Eastern Kingdoms, the Horde has had longer to prepare, and then Contact is made.
The Horde, expanding, come across a savage nation of Elves, who call themselves Kaldorei. Initial conflicts are savage and bloody, only the Tauren have any real knowledge of the Kaldorei, trhough the Cenarion Circle, and there is no Alliance presence on Kalimdor to compare them with. Also there is no Alliance presence in Theramore, the Horde -Can- afford to expand South, and not North, into Kaldorei lands. AFter a very rocky start, relations improve, as after all the Kaldorei and Tauren have very similar belief structures, in fact exactly the same when it comes to Druidry.
The divisions between humanity and elves would not be so great, and Strom and Gilneas in a much better state than in our Timeline. They would likely not rejoin the Alliance of Lordaeron, however with the more similarly minded people of Quel’thalas (in some cases due to oaths spanning millennia). Those three nations would effectively possibly form a Northern Confederacy, a Triumvirate of nations who are neutral, but friendly with the Alliance, yet hostile to the horde.
Things aren’t going so well for Illidan over in Outlands, he doesn’t have Kael’thas and his Sunfury on his side.
By the time Archimonde rocks up at Hyjal, he will likely face three armies, same as he did in our timeline, however these armies would be the Kalimdor Nations (Horde plus Kaldorei Allies) The Alliance of Lordaeron, and the ‘Northern Confederacy’ (Or whatever they would call themselves) of the Kingdoms of Strom, Gilneas and Quel’thalas.
Where history goes from there, is unsure, but it would be a very different world, had Arthas listened to his mentor and his lover…
