SPOILER ALERT: Do not read if you have not yet watched “The Best Laid Plans,” the midseason finale of the sixth season of “Vikings.”

The Rus have officially invaded Vikings territory. On Wednesday night’s midseason finale of the History series, Ivar (Alex Hogh Andersen) and Oleg (Danila Kozlovsky) landed at King Harald Finehair’s (Peter Franzén) doorstep, where he, Bjorn (Alexander Ludwig) and the rest of the remaining Vikings waited to do battle. Unfortunately for them the remining territories refused to answer their call for help, and they were easily outnumbered by the Rus.

By the end of the bloody episode Bjorn had fallen to his brother’s sword and Finehair was down for the count, but according to creator Michael Hirst viewers shouldn’t assume anything. “You don’t know whether Bjorn is dead or not,” he tells Variety.

When the show returns later this year for the final 10 episodes of the series, the story picks up a day or two from where the action left off, with several key players critically injured and Ivar in a state of celebration. But before that happens, Hirst talks with Variety about the historical context behind some of the episode’s bigger scenes, working with director Daniel Grou, and capping the series off in the next batch of episodes.

Did you schedule Daniel Grou’s directing block so that he could specifically helm the midseason finale?

He’s fantastic. He really is a very gifted director and that was pretty carefully planned out because my God, that was a challenging set of episodes. They were hugely imaginative and hugely challenging and he was definitely the person I wanted to tackle that. It meant a huge amount. He’d shot other episodes and he was always comfortable but prepared to take risks. The show just kept getting bigger and bigger and bigger, and he was never phased by that. And he’s a really nice guy.

The final battle was juxtaposed with quiet moments on the beach between the brothers, discussing their father’s legacy and destiny. How important was it to add that personal touch, especially considering that Ivar goes on to stab Bjorn?

The director and I talked about that a lot. We’ve done it before where you get a personal story in the middle of a battle. It just seemed too good a thing not to do — to have these two brothers who’d always locked horns, who represented different aspects of their father, to actually talk together sort of quietly while there’s a battle going on. “Vikings” does that well, I think, in that it’s surreal but almost totally believable because probably in their heads they would have been talking to each other anyway, because they knew that they were fighting each other. I suppose in an opera you’d get that sort of interchange. I love it. I think it works so well and I love the thing that that Ivar says, “The gods must love us because they seem to enjoy us fighting so much.” I hate those battles scenes where it’s just constant armies going from left to right and right to left and you don’t really care who dies. I just want it to be personal. There are lots of personal conflicts going on, personal life and death moments. I always loved those intrusions that I could inject into the narrative.

Were there historical battles or art that influenced the visual storytelling in those scenes?

It would be easy to say something like “Saving Private Ryan.” Daniel and I talked about it a lot and he had a lot of input about how he was going to shoot this big invasion. One of the problems we had to solve was that boats couldn’t run up onto the beach of a Fjord because it doesn’t work like that — there’s no gradually sloping beach. They would just simply smash into the side. So that was a concern. We were talking to Daniel about that and he said, “Well, what if they have the equivalent of a sort of landing craft?” Of course Ivar is with the Rus and knows they can’t land. So he suggested that they develop these shallow boats that are just like the landing craft on the D-Day beaches, except made from the materials at the time. We were learning from history and predicting history, and that was quite exciting that we were referencing the D-Day landings in a TV show about the Vikings.

Some of the narrative in the midseason finale returned to the bigger series’ themes of Christianity and paganism, especially in the new world. How do those themes drive the final back half?

Well, that’s just the deep texture of the show, which has always been about the conflict between paganism and Christianity. That was a real issue, a real event at the time. And that ultimately of course led to all the Scandinavian countries being Christianized. It’s just an issue that I won’t let go of and I put it in as often as it seems appropriate to do so, just so the audience doesn’t forget that this is the backdrop. I keep those issues very much alive. I’m interested in spirituality from both the Christian and the pagan perspective, but I’m interested, too, in how that affects politics and civilizations. There’s always a political angle to everything, but hopefully too, there’s a sense of people with real beliefs that drives them, and I can promise you that in [the second half of Season 6] certain things happened that are quite astonishing and that bring all those things completely back to the forefront of the show in an amazing way.

What does it say for the Vikings and their future that they wouldn’t come together to fight this opposing enemy?

There’s an attempt to recognize a new reality that as they face bigger, more powerful enemies, they ought to at least make an effort to combine and to possibly stop these endless squabbles and rivalries between small kingdoms. So that obviously is a subject that we explored and the attempt is made to do that. But this tribal culture is very deep-rooted and it doesn’t go away in a generation. Harald Finehair was in fact the first king to be anointed King of all Norway. That’s in the show too, and that’s true. But it just doesn’t tend to work for them. It would have been better if Bjorn had been elected King of all Norway because of the prestige of his father and his family. But it’s just an ongoing issue that it is not resolved during my stint as a writer of “Vikings.” They still fight each other. They can’t help it.

Speaking of Finehair, there was the tough scene in which he rapes Bjorn’s second wife, Ingrid (Lucy Martin), in what seems to be an act of taking what he believes is rightfully his. That was the custom at the time, but what kind of a treatment do you need to give a scene like that in today’s climate?

It’s not a good idea for a writer to become too self-conscious and to try and second guess what people would approve or not approve of these days. I’ve never been exploitative of the characters, I hope. I don’t think I have in that or in any other ways, but at that period it was possible for Kings and possibly other important men to have more than one wife. There are sexual politics that, the results of which are, incredibly powerful and revelatory. And I can’t speak too much without giving it away. But Gunnhild (Ragga Ragnars) is confronted with a terrible choice, and the choice she doesn’t want to make and how she deals with this choice is fantastic and totally admirable and wonderfully moral in all sorts of ways and very, very moving. I can’t tell you more about it, but I do assure you that when you see how she deals with this incredible, incredibly difficult and compromising situation she’s placed in, in which she’s supposed to marry two men, the way that she deals with that is incredibly moving and brilliant. I’m actually rather proud of it. I must mustn’t tell you anymore.

Will there be a return to Wessex in the back half?

Yes. Big time. Big time. There are a lot of contexts here that I don’t want to go into but essentially, it’s Ivar deciding there is unfinished business in Wessex, that he has unfinished business with Alfred [Ferdia Walsh-Peelo]. So there is another Viking army that goes to England and the battles and the warfare is pretty pivotal in the history of the show and also the history of the real Vikings. There are big set pieces and there’s a lot to play for. By this stage, when they go back to England, Wessex is the last Saxon kingdom left. Every other kingdom in England has fallen to the Vikings. So the stakes are extremely high.

Is Kattegat as something to conquer still in play?

Kattegat will always feature. There are many, many interesting twists and turns in the story of Kattegat and who rules Kattegat and who ends up ruling. And not in a million years would you ever be able to guess who ends up at the end of the series ruling Kattegat. But Kattegat is the spiritual and physical home of my Vikings. So it always had to play a central role in the drama.

At the end Erik (Eric Johnson) runs off with the crown, what is that significance?

It is important that he took off with the crown because he becomes a sort of kingmaker. There was a man in the real Wars of the Roses in England called Warwick the Kingmaker because whichever side he favored could take the crown. Erik is, slightly in that tradition, going to be a Kingmaker, in that he’s going to try and decide who’s ruling in Kattegat and who’s ruling perhaps in other places. He has a very inflated idea of his importance. He is quite an ambiguous figure, I think. He may not be quite the person that we think he is at first. But his role does develop and it is important.

Watch more with Alexander Ludwig from “Vikings”: