When a film franchise's most iconic piece of imagery is an awesome weapon (read: a lightsaber), it only makes sense to deliver on epic fight scenes. Star Wars: The Last Jedi treats viewers to a few amazing action sequences, but one is particularly unforgettable: the battle that takes place in Supreme Leader Snoke's sleek red throne room. It culminates in Rey and Kylo Ren fighting over Luke Skywalker's former lightsaber - which ultimately splits in half. But why does that happen?
After Rey and Kylo spend some time communicating via Force link, she believes that she has the ability to pull him to the light. She boards Snoke's ship, the Supremacy, only to be captured and presented to the First Order leader, who admits he set up the communication bridge for manipulation purposes. He also takes information about Luke's whereabouts from Rey's mind and urges Kylo to kill her. Instead, Kylo deceives his superior and kills him. What follows is a stunning display of unexpected teamwork in which Rey and Kylo work together to take down Snoke's elite Praetorian Guards.
But Kylo is, of course, not so easily turned. He tries to get Rey to join him in forgetting the past and ruling a new world and even drops the long-awaited truth-bomb about her parents. However, she declines and uses the Force to reach out for her lightsaber, which she'd tossed to him for help in the fight. He doesn't take the rejection well and does the same until they're at a tense game of Force tug-o'-war with the lightsaber. Soon after, it splits in two.
The Force Awakens and The Last Jedi both repetitively assert that Rey and Kylo are extremely powerful Force users. It makes sense, then, that the lightsaber breaks in half due to not only how much power they're using, but also because they're evenly matched in using said power. But does something else have a hand in causing disarray to the throne room?
Afterward, we see Vice Admiral Holdo sacrifice herself to ensure that the Resistance can escape their enemies. She sets the Raddus to hyperspeed and flies it directly into the Supremacy, causing the First Order ship to split in two.
Visually, this occurs after the lightsaber breaks. While it's possible it may actually happen during Rey and Kylo's showdown, it seems to have little effect on it. The throne room is shown in shambles during and after the guard battle, again likely due to Rey and Kylo's sheer strength.
Regardless of the sequence of events, it's interesting to note that this portion of the film features quite a few things splitting in two - the lightsaber, the Supremacy, and even Snoke himself, whom Kylo bisects. None of these things necessarily need to have such clear-cut divides, but they add a little something to the overarching theme of duality in the film. Many of the characters constantly struggle with two sides, like light vs. dark and failure vs. success, making all the splitting a nice visual reminder of what the whole movie is about.