Way back on my first character (who was -not- Tatia) I quested in Elwynn forest and eventually moved into Westfall. I read all of the quest text and paid attention to the story. At some point I got a quest sending me to Westfall.. and I remember reading about some NPC commenting how Westfall is overrun with Defias because everyone else has gone off to the war. At the time I wondered what level I’d have to be to catch up to the war front.
I kept thinking, maybe it’s in the next zone.. maybe suddenly I’ll stumble across the warfront.. Horde NPCs facing off with Alliance NPCs.. a huge battle.
I’ve never found the front.. in fact at this point I’m pretty sure it doesn’t exist. It’s just an unsatisfying answer.
The elite guards of flightpaths/towns in contested areas and the NPCs inside some battlegrounds (well ok, AV) are the only real signs of a war.
AFAIK, the Alliance and Horde have a fragile peace after the third war with some skirmishes (the various PVP zones and world PVP) by the more hot-headed individuals on both sides.