The opening of the film Spectre is a single, eight-minute shot that starts with James Bond in a skeleton costume watching a Day of the Dead parade on the streets of Mexico City and ends with him in a perfect-fitting suit striding along the edge of a rooftop as he finds his target. That shot is inextricably linked to the new World War I film 1917, and not just because both films were directed by Academy Award-winning filmmaker Sam Mendes. While he was shooting Spectre, Mendes was also developing the idea for 1917, his next film.

"I was excited doing the opening shot of Spectre," Mendes said during an interview at CNET headquarters in San Francisco. "It was an exciting experiment and I thought, 'Wouldn't it be extraordinary to make a whole movie in this way?' But I never thought I would actually do it."

1917 is about a pair of British World War I soldiers on a mission to deliver a message that could prevent 1,600 men from heading into a deadly trap. The idea behind shooting the film as a continuous single shot was to constantly link the audience with the two young soldiers as they traverse the trenches and fields of France.

Fortunately, Mendes had by his side Academy Award-winning cinematographer Roger Deakins, who is camera royalty having shot most of the Coen brothers films as well as movies like Skyfall, The Shawshank Redemption and Blade Runner 2049, for which he won an Oscar. He is to cinematography what Lennon and McCartney are to songwriting.

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The cast of 1917 includes Benedict Cumberbatch, Colin Firth and Andrew Scott (aka Hot Priest from Fleabag) in supporting roles, leaving the leads to Dean-Charles Chapman, who you might remember as Tommen from Game of Thrones, and George MacKay who was in the film Captain Fantastic. I should also note that Chapman's mullet-ed performance in the film Blinded By The Light is absolutely wonderful.

Mendes, Deakins, Chapman, MacKay and screenwriter Krysty Wilson-Cairns joined CNET Editor-In-Chief Connie Guglielmo and me to talk about their latest film. We discussed numerous topics including the challenges of filming in a single shot, how Mendes used his theater skills to direct scenes, making movies on an iPhone and the role research played in keeping 1917 authentic. Here's an edited transcript of our conversation.

1917 is described as an epic war film that takes us through the trenches of WWI. What's the story about? 

Mendes: The movie is about two men who were tasked with delivering a message across no man's land and into German territory that will potentially save the lives of 1,600 men including one of the men's brothers. What happens to them in two hours of real time is shot as one continuous shot. It was inspired by stories my grandfather told me. He fought in the war as a 17-year-old, but didn't talk about his experiences until his seventies. One particular story he told about a man carrying a message was the germ of this movie. And Krysty, the screenwriter, took that idea and thought, "Well, what if that man kept going and that man became two men: Scofield and Blake?" And that's how we came up with the idea.

Why is it important to tell this story now?

Mendes: It's a good time any time for a story about the human experience of war. Even though you don't need to know anything about the first World War to see this movie, it is now over 100 years since the war ended. It was a war that changed the world, changed the shape of Europe. Boundaries were redrawn. It was the first modern war. It started with horses and carts and ended with tanks, machine guns and weapons of mass destruction. And there's a danger of it being forgotten as it disappears into the mists of time.

We're now living in a time where there aren't any living survivors of World War I. I felt at one level it's a duty, but I wouldn't say that I made it to teach an audience a lesson. It's an experience.

You're quoted as saying your choice to have the film take place over the course of one day was because there's something pure about it. Can you talk about that?

Wilson-Cairns: We wanted to tell a story that felt immersive, so choosing to do it over one day and to do it in real time strips away all the artifice of cinema. That came from Sam. It was his idea of telling it in real time, of telling an immersive war story in which you don't actually need to know anything about the war. You just need to know you follow these two men as they do everything to try and save someone they love. It stands outside of the genre and outside of time.

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Krysty, can you talk about the writing process? I imagine trying to time a scene with two people walking and having the dialogue land at certain places has to be a challenge. How did you figure that out? 

Wilson-Cairns: We never actually approached the story from a technical point of view. It was more how could we show what it was like to be human in this war? So that was the basis of it, and then in the rehearsals, obviously, timing and everything else came into it. And that involved a lot of us in fields with flags running around looking strange I would think is the easiest way to describe it. But yeah, if at the beginning of it Sam had in his head that this scene has to be 22 seconds long I might have hit him because that's not what writing is.

Tell us a little bit more about these characters and what you did to get inside the mind of a British soldier from World War I.

Wilson-Cairns: I did a huge amount of research. I read a lot of firsthand accounts. I went to France. I pretty much went to every World War I museum I could find. And that's just the job of a writer. You're trying to unlock a character and you don't need to be a man or a woman or a soldier to get into that. You just need to want to have an understanding of their experience.

The two characters are very different. For Schofield (George MacKay), he's been out there in France a bit longer than Blake (Dean-Charles Chapman). He's seen action and he's been profoundly shaped by that. But even before that, he has sort of a quieter mind. He's more self-assured and more interior. Whereas Blake is younger. He's green. He's probably never been in any real action. My idea of him on the page was always that he wanted to be a hero. He's maybe read The Lone Ranger or something like that. He dreams of going out there, storming the world, winning a few medals and being loaded. And so they're two very different characters at the beginning of the movie.

Dean, were you the Lone Ranger in your mind? 

Chapman: Blake's backstory in my own head was that he joined the war in the first place because his brother joined first. Blake is a very family oriented person and he admires his brother more than anybody. But yeah, he definitely wanted to see some action and go on an adventure. Not a lot of people in that era went to different countries, let alone outside of the city. Blake wanted to see more of the world.

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1917 was filmed to look like one continuous shot. How did you decide upon that approach?

Mendes: Once I decided the movie was going to be two hours of real time, it seemed like a natural thing to try to lock the audience together with the characters in a way that they couldn't escape so that they experience every second passing with the men. It's essentially a race against time. It was an emotional decision as much as anything else. Even though we shot it in one shot, I don't think Roger and I particularly want the audience to be thinking about what the camera is doing. We want them to be lost in the story. 

In one of the interviews you did about 1917, you said you had to convince Roger about doing the film as a single shot. Roger, how hard was it for Sam to convince you? 

Deakins: He didn't tell me about it. He just sent me the script and said it was World War I, which had me sold straight away. But on the front page, it said this is envisioned as a single shot in real time. It was a bit of a shock.

Limiting yourself to one shot seems like it would challenge a lot of the norms of filmmaking, like reverse shots and lighting. How did you work around those limitations? 

Deakins: There's always limitations with any film you do. It's particularly challenging to work out where you want to put the camera and how to show the audience what you needed to show. But I don't know how different it is from any other movie. You're just doing it in sections and building them all up really. 

Mendes: You're trying to find a constantly evolving style for the camera, so it doesn't get trapped in one position all the time. And sometimes it's very intimate. Other times it's very epic. Sometimes you want to see that you understand certain geography and distance and space. Sometimes you want to understand the mood and shift the atmosphere. You're trying to use all the tools you would normally have as part of film grammar, establishing shots, close-ups, but within one continuously moving shot. So the relationship with the camera and the characters is constantly changing. The thing was to try and develop our own particular language for this film. But as Roger says, that's what you do for any movie, just on this one we had to do it within the same continuous snaking movement. 

Deakins: It was interesting. The first film we did together, Jarhead, was all handheld. We basically shot the rehearsals. And then we decided, "Well, that worked here, why don't we do this shot ... now go around this way. We need to cover it this way." It was very spontaneous on the moment of the shoot.

Whereas this, we had to work it out absolutely to the nth degree before we could do anything. You had to know the length of the trench before the trench could be dug. What was crucial was having the actors and having that space in pre-production to really work out what those shots were. But hopefully the effect is no different from Jarhead. It's immersive. It's a different technique. But still the aim is not for the technique to overtake the story and the emotion in the story.

Roger and Sam, Steven Soderbergh has famously shot films using an iPhone. Would you ever use a phone to shoot a film?

Deakins: I shot part of a film on an iPhone. In The Valley of Elah had a whole sequence on an iPhone. Yeah, why not?

Mendes: These days cameras are getting so small. The camera we shot this on was a prototype Roger worked on with Arri. It's the Alexa LF, but it was a Mini. So it's not much bigger than a transistor radio, really. I mean, it's a little bit bigger. As that reduces, you've got IMAX scale images that you're shooting on a smaller and smaller piece of equipment. So, give it 10 years, it probably won't be much bigger than an iPhone. That's the truth.

George and Dean how did you find filming single continuous shots for your scenes? Was there one of you who caused more retakes than the other?

Mendes: They were both in it together. So you couldn't blame one or the other.

MacKay: Yeah, we come as a pair. Between my water bottle and his flag…

Mendes: Oh yeah, [to MacKay] your water bottle that was a nightmare. And [to Chapman] your flag. The two nightmare props. 

MacKay: It was a wonderful experience filming in this way. It was a real lesson in having a much more three-dimensional understanding of the filmmaking process as a whole but then also our role within it. Some of the time there are actors where there's almost a fabled thing of like, "You're in your character." And it's like you, you you. The best thing you can do is to have no awareness of anything other than what your character should be doing. And that is valid at some points but everyone's always working together. And this, all the more so, was the complete embodiment of that. It taught us both to have an inside/outside perspective on the scene. It has been a really healthy lesson, at least for me as an actor in moving forward.

Chapman: I've never really had any kind of experience similar to the making of this film. Even though it's immersive for an audience member to watch the film, in the doing of it, it was really immersive. We were the ones that were there. Everything you see on the screen, we were going through. The conditions were realistic. It never felt fake or acted. It felt very lived. Dennis Gassner, the production designer who created the sets, did an amazing job bringing those to life and as an actor that's a dream come true when you can just get lost in the scene.

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You basically re-created the trenches of World War I. You literally built that experience. I don't know how much mud you had to create for this…

Mendes: It was England. There's a lot of mud.

...but people have been inundated with images of war and some people are desensitized to it. You actually kind of lived through that war as you were shooting it. What stood out from that experience? 

Mendes: You want to make it as real as possible. It's the details that you're looking for. The details in photographs, details from first-person accounts. You're trying to reimagine something and not use other movies as your touchstone. People feel they know what the '30s were like. But do they really? Or do they just know what movies from the '30s look like? People feel they know what the first World War looks like. But is that really true? Or is it just a set of images that are just other versions of reality?

We went back to photographs and studied them endlessly. And however much you work to re-create environments, and they were pretty real and sometimes grim, it was nothing compared to what the real men lived through. Even though we were re-creating conditions, most of the time we couldn't even stand up. The mud was like standing on ice. You just fell over all the time. Nobody ever complained because what's three weeks in the mud when these men spent three years living in it.

But it was sobering to understand the degree to which they were stacked. They were trapped in this environment for years. And like you say, sometimes one could get desensitized. But part of the job of this film was to take us out of the things that we commonly associate with World War I (mud, trenches, No Man's Land) and into different environments that still express the scale of the war, the scale of the destruction, the loss of life, on such a vast and cataclysmic scale. I suppose if there's a philosophy in it, it's that through the micro, you can understand the macro somewhat. Through the keyhole of two men's experience, you can begin to understand the scale of the destruction that happened over the course of four years and the greatest loss of life in any single war.

MacKay: What you said about being desensitized to it, I don't think we really understand because that would suggest that you knew it in the first place and that's gone away. That's why Peter Jackson's film was so amazing. We suddenly saw it in color and went, "They're like us."

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How did you go about developing your characters?

Chapman: I read a lot of first-person accounts, diary entries and letters written back to home just to get into the headspace of a soldier back then. I watched the Peter Jackson film They Shall Not Grow Old. There was also a photograph of three soldiers. Two of the soldiers standing on either side were very straight, very serious. Sort of your typical World War I soldier in a black and white photograph. But there was one soldier in particular that was standing in the middle of the two soldiers leaning up against the truck. And he had his jacket undone and the shirt was all twisted. He was smiling. He had no teeth, and he had his hand on his chest. On his hand, he was wearing a ring on his pinky finger and a ring on his middle finger. How relaxed he was, and his personality oozing out of this photograph just reminded me of Blake. So I made Blake wear the two rings. Every time I think of Blake for some reason I always think of the rings.

MacKay: In terms of Schofield, his home and what it means to him and the chinks that you get of that and how and why he can and can't talk about it was essential for me to know. And then also his experience of the war so far was another thing that shaped his way of being. So I, for myself, just through research and imagination had to kind of work out what that was for him.

The credits listed a weather manager or chief meteorologist. What was his role? And how did weather play a role with lighting and continuity?

Mendes: We couldn't shoot in the sun and we couldn't shoot in the rain. We needed cloud cover for the majority of the film until it went to night, and so we did spend a lot of time second-guessing the weather. When the weather was bad, we'd rehearse and rehearse and rehearse and perfected the shot, and soon as the weather cloud came over, we went. And sometimes that was a good thing because it adrenalized everybody. We knew we had a limited window of time in which we could get the shot. But we did have a lot of discussions, not me personally, with weather gurus. There are a lot of people studying apps telling us when the clouds were coming over, all that sort of stuff. And I believe he was our chief weather guru. I can't claim to have ever met him personally, I'm not sure whether Roger did either.

Deakins: He was the local weather guy down in Salisbury as far as I understand. But I know I had like four different apps on set I would look at to see the radar of when the clouds were coming in. And I spent a lot of time looking at the sky. 

Besides being a continuous one shot, 1917 is also unusual because you shot the film in order, right?

Mendes: Yeah, we did shoot it mostly in sequence, which is an unusual luxury for a movie. I mean, normally, you're fragmenting the story all the time. And one of your jobs as a director is to remind the actors where exactly they are in the story -- not necessarily physically you know ... but emotionally. So it was actually easier because it was a physical continuity for most of the time. There are a couple of sequences we shot out of order. But mostly we started at the beginning and went on till we got to the end.

Having directed a lot of work in theater, how did those skills come into play during production and pre-production? 

Mendes: I had to make judgments about rhythm and tempo and the momentum of the story without cutting. And that's something I do in the theater all the time. Judging shape and when the movie could breathe in and breathe out, that's something that one does with stage productions. So that muscle I was using every day because there was no way out. And there was no way of taking a line out, let alone a scene or moving the order of something. Nothing like that. Everything had to be exactly as I'd want it in the final movie. So I was using that part of my brain that I would normally use in editing, in production. But in another way, the movie was completely cinematic and very unlike theater. The conditions are constantly changing, constantly shifting landscape, constantly shifting the relationship between the audience and the characters in a way that doesn't happen in theater. 

Was there a particular sequence that was incredibly challenging to get in one take?

Deakins: The last shot of the film because we wanted the sun to come out. It was the hardest shot in the film.

Mendes: And it did.

I was still thinking about the opening and last shot two days later. Was that something scripted?

Wilson-Cairns: The opening was always meeting Blake and Schofield tired. We didn't want the sense of them beginning a journey, we wanted the sense that you caught them halfway through a journey. So they're two exhausted men at the start of this. Then, obviously, far more pressures are heaped on to them. But the last shot, as much as I would love to take credit for it, was actually reality seeping into the film.

Mendes: Originally I conceived it that George's character was sitting at the banks of a stream and feeling the sun on his face for the first time. And then this beautiful tree emerged in the landscape when we were scouting and it felt like that was where he should go. Somehow it seemed right that he came full circle. But it'd be wrong to think that he was the same man at the end of the film that he was at the beginning. He's aged many, many years in the space of the few hours he's been traveling. In a way, it asks you to compare the two: the man at the beginning and the man at the end and reflect on the experience he has been through.

Originally published earlier this week.