vzphotos/iStock(NEW YORK) — It’s still anybody’s guess as to who will win the Oscar for best picture Sunday night, but many oddsmakers are predicting it’ll be the World War I drama “1917.”Written and directed by Sam Mendes, who is also up for best director and best original screenplay, “1917” tells the story of two British soldiers faced with a seemingly impossible task: cross into enemy territory to deliver a message calling off an attack. If they’re unsuccessful, 1,600 will die, including the brother of one of the main characters.“1917” has an 89% approval rating on the criticism aggregation site Rotten Tomatoes, and according to Box Office Mojo, has earned more than $253 million worldwide since it was released last December. (It went wide on Jan. 20.)Already the winner of the Golden Globe for best dramatic motion picture and best director, here are a few other things you need to know about the film.1. It’s based on personal stories: Mendes told ABC News at the Oscars luncheon last month that the story is based on tales his grandfather told him when he was a child. “It was me and my cousins pestering him, thinking we were going to hear stories of heroism and bravery and how he won his medals and it was going to be cool, and instead, he turned around and told us stories of absolute chaos and the randomness of how thin the line was that separated him, who stayed alive, from his friends who all died alongside him,” Mendes said. “He told one very memorable story of dragging a man back through no man’s land who was pleading with him to leave him there saying, ‘I’m dying. Don’t pick me up. Save yourself.’ But, my granddad dragged him back on his own back. And when he put him back down in the trench, when he finally reached the end of the journey, he laid him down and realized that he was already dead and he had been shot while he was being carried. But had he not been carrying this man, he himself would have received the bullet. So he was effectively carrying a human shield.”“You never know, as a storyteller, or as a filmmaker, what’s going to grab you or not let you go,” he continued. “And this wouldn’t let me go.”2. It doesn’t look like anything else: “1917” earned 10 Oscar nominations, more than any other film, including best picture, best director for Mendes, and best original screenplay for Mendes and Krysty Wilson-Cairns. Many critics believe Mendes has a great shot at best director, largely because of how the film was shot. “I always felt once I had decided that it was going to be two hours of real-time, that the story was going to be told in a very, very condensed time period. It seemed a natural thing to not have any cuts,” Mendes said. “For me, the process of editing very subtly and in tiny ways can take you out of a sense of real time, a sense of believing that these people are crossing a landscape and that you’re living and breathing with them. You’re experiencing every second passing in what is effectively a race against time and you’re watching them take every step and you’re going to have to take it with them. So, it felt like a way of locking in the audience with the characters so they couldn’t escape.”3. The cast and crew prepared for a very long time: Mendes told ABC News that pre-production was “very lengthy and very detailed.” “Every step of the journey had to be constructed. Every trench had to be measured, the exact length, every orchard, every farmhouse, every town street had to be exactly the right length of the scene because there was no way of cutting distance or jumping time,” he explained. “There were some pretty absurd occasions when it was just me in a field with the script, trying to say the lines at the speed at which I thought they were going to be spoken. Or even in one case, just running and throwing myself to the ground and getting up and running again for another 40 yards. And the frame was hooked down again.” Ultimately, he said they built more than a mile of trenches, which was “very exhilarating to watch it just grow and grow and grow.” Meanwhile, the actors did historical research, traveled to France and examined the original sites, he said.4. Some unscripted moments made the final cut: While much of the film was meticulously planned, plenty of it wasn’t. “At the end, if you’ve seen the movie, Schofield, played by George MacKay, has a final run and he gets knocked off his feet, not once, but twice, neither of which were planned,” Mendes said, adding that they were often left to contend with the elements, too. “I said, ‘If… you get knocked off your feet, just get up and keep going and we’ll see what happens.’ I always said to them, ‘Just remember, it’s not you slipping in the mud, it’s your character slipping in the mud. It’s not you. If you fumble over a line, it doesn’t matter.’”5. It took a while for Mendes to realize what a success it was: A passion project from the start, Mendes wasn’t sure that “1917” would resonate with audiences until it began previews. “There’s a particular kind of energy that exists in the room when something is really gripping an audience, and … after about half an hour, I thought, ‘They’re with this,’” he recalled. “All this awards season hoopla is great and it’s a wonderful thing for everyone who’s involved in the movie, but at the end of the day, what matters most to me is that audiences turn up to see this in the movies. Given the fact that it’s a very big, ambitious film, it’s not a franchise. There’s no existing IP, and it doesn’t have two giant stars in the leads.”“And so the fact that it’s connected with audiences is incredibly moving,” he continued. “Having lived with it for two years and lived and breathed it every second for that time, to watch it then take off and people embrace it has been a great thing.”Copyright © 2020, ABC Audio. All rights reserved.