Game of Thrones set up season 8's Battle of Winterfell all the way back in season 2. HBO's fantasy drama may be all about plot twists and surprise deaths, but the more that fans explore this world, the more they see that many of the biggest moments may have been foreshadowed (or even spoiled) well ahead of time...
The Battle of Winterfell, the biggest on-screen battle ever that will see the armies of the dead and the living finally come together, definitely isn't a twist - Game of Thrones fans have been expecting the White Walkers to face off against the armies of Westeros since they were first introduced. However, fans may be surprised to look back and realize that it was originally mentioned in the show as early as the second and third seasons - thanks to Melisandre and her visions in the flames.
The first potential mention of the Battle of Winterfell may have been in the season 2 finale, "Valar Morghulis", when Stannis first saw a vision in the flames. This is after his resounding defeat at the Battle of Blackwater, when Stannis is still reeling from the loss of his fleet and most of his army. He attacks Melisandre, and nearly kills her, before she shows him something... and while it isn't immediately clear what that is, it's enough for him to keep her at his side, to keep fighting - and to head North. Later, in the season 3 episode "Second Sons" (episode 8), Stannis reveals to Davos what he saw: I saw a vision in the flames. A great battle in the snow. I saw it.
It's possible, of course, that the battle Stannis saw was his own fight in the North, the one that eventually cost him his life. However, when Melisandre returns to Castle Black after that battle (and Jon Snow's "death") fans are given a little more information about Melisandre's visions of a snowy battle. While standing over Jon's body, Melisandre says "I saw him in the flames fighting at Winterfell". At this point in the series, Jon had never fought at Winterfell - he had only been at the Wall.
Again, it's conceivable that this battle is the Battle of the Bastards, however, that battle was technically fought just outside Winterfell, while the Game of Thrones season 8 Battle of Winterfell is going to take place inside the castle walls. It's also worth pointing out that there would be little reason for Melisandre to have visions of the Battle of the Bastards rather than any other major battle - she has been searching for the resurrected Azor Ahai since the first season, who is connected to the White Walkers and the fight for Westeros. The Battle of the Bastards, while incredibly important in the grand scheme of Westerosi politics (and in making Jon Snow the King In The North), isn't directly connected to the fight with the White Walkers, whereas the Battle of Winterfell is. She does reference visions of seeing the banners of the flayed man falling, but there is no reason to think that these two visions are the same - especially because the Battle of the Bastards didn't involve snow - something else that she has said she sees in the flames, which Stannis saw as well.
Put all of this together, and it seems clear: the battle that Melisandre has been seeing in the flames since the start isn't a battle that Stannis fought or the Battle of the Bastards. It's Game of Thrones season 8's biggest battle of them all: the White Walkers against Jon Snow's forces at Winterfell. Of course, Melisandre isn't exactly the best when it comes to interpreting her visions, but that doesn't mean that they aren't accurate... and that those first hints of the Battle at Winterfell haven't been dropped from very early on.
Game of Thrones returns for its final season on April 14 on HBO.