The "Battle of Haven", also known as the "Attack on Haven", took place at Haven Academy across the episodes "The More the Merrier", "Vault of the Spring Maiden", "Downfall" and "Haven's Fate" in RWBY Volume 5.
Raven Branwen forms a deal with Cinder Fall and her allies to lure her brother Qrow Branwen and his allies into a trap, with Cinder seeing this as an opportunity to capture Ruby Rose as well. Raven later convinces Haven Academy headmaster Leonardo Lionheart to call Qrow.
Meanwhile, with information that Adam Taurus is planning to attack Haven on the night of the last full moon before students return to school, as well as thwarting an assassination attempt on her parents' lives, Blake Belladonna rallies the Faunus of Menagerie to help go to Haven and help protect it from the impending White Fang attack.
Professor Lionheart is waiting for Qrow in the front hall of Haven Academy when Qrow and the rest of his team show up. While he questions why they came armed and with so many people, Yang Xiao Long notices a raven sitting in the corner of the room. Spotting it as well, Qrow fires a shot at it, but the raven avoids it and transforms into Raven Branwen. Raven reveals that Leonardo has actually been in league with Salem, but defends his actions as justified when Qrow becomes outraged at his betrayal. When Qrow deduces that his sister has the Spring Maiden, he tries to convince her to join their cause, only for Raven to angrily rebuff his request. When Ruby tries to get through to her, Raven remarks on how much she sounds like her mother before cutting open a portal, allowing Cinder, Emerald, Mercury, and Vernal to enter, the former of which immediately strikes Ruby with a fireball just before she and her allies enter the room.
Shortly afterward, Hazel Rainart enters the hall, revealing that the White Fang has begun setting up explosives around Haven Academy, and proclaiming that nobody will be entering or leaving. Outside, Adam is seen organizing his forces for Haven's demolition.
When Qrow becomes angry with Lionheart and his sister for their betrayals, Cinder mentions that while Raven was a recent addition to their side, Leo had been feeding them information for a long time. This, however, is interrupted by Jaune Arc, who begins going on an emotional rant questioning how Cinder was able to take so many lives and yet go on to rub it in their faces. As Jaune declares that he will have his revenge, Cinder responds by stating that she doesn't even remember him.
Furious, Jaune recklessly charges and engages the Fall Maiden in melee combat, while Ruby attempts to help him before getting intercepted by Emerald Sustrai. Yang is confronted by Mercury Black, who taunts her, while Qrow starts a fight with Raven while angrily disowning her. Raven commands Vernal to attack Weiss Schnee, but to withhold her powers. As Vernal does just that, Hazel is confronted by Nora Valkyrie and Lie Ren before stating that he doesn't wish to fight. As Ren and Nora remain undeterred, Hazel cracks his knuckles and engages them in combat.
Oscar Pine climbs the stairs and confronts Leo. Unaware of who Oscar really is, Leo warns him to leave. When Oscar continues to advance, Leo deploys his weapon and attempts to fire a flaming rock at him, but Oscar absorbs it with his Aura as he deploys his cane. A terrified Leo quickly realizes that Oscar is really a reincarnation of Professor Ozpin, and Oscar handily batters him around using his cane. Leo expresses surprise that Ozpin had reincarnated already and that Qrow had found him so quickly, and becomes determined to capture him in order to please Salem. As Oscar asks what to do, Ozpin reassures him that they must fight.
The fighting cuts back to Weiss battling Vernal, where Vernal keeps the pressure on with her constant fire and flinging of her blades. Weiss attempts to summon her Knight several times, but all are interrupted by Vernal. As Cinder and Jaune continue their fight, Ruby attempts to reason with Emerald, only for her to declare that while she doesn't care for Salem's antics, she is absolutely indebted to Cinder. She uses her illusions to confuse Ruby, almost causing her to shoot Weiss by accident. As Weiss continues fending off Vernal, she attempts to summon the Knight once again, but Vernal interferes by hitting Weiss with point-blank beams, instantly depleting her Aura.
As Jaune watches on in horror, Cinder mocks him by asking if he will allow Weiss to die too. Jaune angrily tells her to stop messing with him, only for Cinder to grant his request by shattering her blade and forming a sword of pure fire. As the two charge, Ruby has a flashback to when Pyrrha Nikos died and manifests her Silver-Eyed powers. However, Emerald takes the opportunity and knocks her out cold.
Jaune looks up to realize that Ruby's outburst caused Cinder to fall to her knees in pain. Jaune immediately goes in for a strike, and while Cinder dodges it, his sword manages to scratch a bit of her face mask. Outraged, Cinder begins a relentless attack on Jaune, only for him to say that his death won't matter if he manages to buy his friends time. Just to spite his declaration, Cinder throws a flaming javelin at the wounded Weiss, fatally impaling her while Jaune watches on in horror.
As Oscar sees Ruby knocked out, he becomes angry and knocks Leo down the stairs. As Hazel criticizes him for letting a mere child knock him around, Leo tells him how Oscar is Ozpin's reincarnation. Seeing his cane as empirical evidence of Leo's statement, Hazel visibly struggles to contain his rage before yelling Ozpin's name. Declaring that Ozpin will pay for what he's done, Hazel injects himself with Lightning Dust. As Oscar asks what to do, Ozpin simply tells him to run.
Cinder and her associates express disbelief that Ozpin is already back, but she has Lionheart open the Vault so that she, Raven, and Vernal may enter. Yang attempts to stop them but is cut off by Emerald and Mercury, who declare that she must go through them in order to get to the Maidens. All this time, Jaune and Ren are trying to bring Weiss back but are having no success until a strange light begins to pour from Jaune's hands, healing her.
As the Dust-charged Hazel begins beating a stubbornly combative Oscar back, Ozpin reveals that Hazel is so angry due to a long-standing grudge having to do with his sister's death on one of Ozpin's training missions. While a question of whether his sister knew the risks of being a Huntsman stops Hazel momentarily, Hazel prepares to finish Oscar before Ozpin forcefully takes over his body, enraging Hazel further. As Ozpin rapidly turns the tides on Hazel, Leo attempts to get a cheap shot in on him before Qrow engages him in combat. Ozpin quickly has Hazel on the defensive before Leo shoots him in the back, forcing Qrow to jump in and save him from Hazel while sustaining heavy damage in the process. Now awake, Ruby tells Jaune to keep up whatever he is doing before jumping in to help her sister fight after witnessing her being cornered by the combined forces of Emerald and Mercury.
As Ruby and Yang fight back against Emerald and Mercury, Nora remarks on how Jaune unlocked his Semblance. When Jaune remarks that he is actually transferring his own Aura to Weiss, Nora expresses concern over how much he has left, only for Jaune to dismiss it. Meanwhile, Hazel punches Ren into a wall and electrocutes him before turning the tables on Ozpin, angering Nora. When she goes in, Hazel grabs her and attempts to fatally electrocute her. However, Nora's Semblance causes her to absorb the electricity and flip Hazel. When Ozpin warns her that his Semblance allows him to nullify pain, Nora dismisses it before using her weapon to smash him through the building, sending him crashing in front of a stunned Adam. As Adam watches on in disbelief, Hazel proceeds to inject himself with Fire Dust in order to combat Nora.
Blake reveals herself on a rooftop and reveals that not only has she successfully rallied an army of Faunus to protect Haven, but she has also called the Mistral Police Force on him. When Adam realizes he is cornered, he attempts to detonate his placed explosives to kill them all. However, Blake also reveals she had already sent Ilia to defuse the bombs. Utterly foiled, abandoned by Hazel and with nowhere to go, Adam recklessly charges Blake, only for her to avoid him and hit him into the ground. A furious Adam orders his troops to kill the Faunus army, and a fight breaks out. Hazel is impaled by a recovered Weiss' new Queen Lancer summon and dragged into the hall, only for Blake to realize that her friends are here. After a short, silent reunion, Yang rushes into the Vault, discarding her mechanical arm in the process, while Blake returns to combat.
Meanwhile, all the White Fang is easily overwhelmed by the combined force of Mistral's police and the Menagerie fighters. After a short fight with Sun and Blake, Adam decides to retreat by himself, the Mistral police chasing after him, their lights focused on him as he flees.
Back in the Grand Hall, the fighting continues as the initial group starts to tire and Hazel and Lionheart manage to destroy the Queen Lancer while Blake joins her friends in the room. Ruby shoots Lionheart and manages to break his Aura, prompting him to flee, but he is confronted by a Seer Grimm commanded by Salem in his office. Despite Leonardo's pleas that he can still be useful, Salem kills him with the Seer.
After a heated argument, Yang convinces Raven to abandon the Relic and retrieves it herself. She goes back up the elevator to the Grand Hall to show everyone the Relic.
Realizing that her master Cinder is gone, Emerald inadvertently unleashes her Semblance to create an illusion of Salem and faints from overexertion. Hazel and Mercury use the commotion to make their escape, with the former carrying Emerald on his shoulder as they run from Haven.
Oscar was able to relay a message from Ozpin to take the Relic to Atlas just before passing out from exhaustion, and Ruby, Weiss, Blake and Yang have a peaceful reunion together. The White Fang is left leaderless and divided, with Haven Academy still standing, albeit without a Headmaster.
Between the time of the two weeks that passed after the Battle ended, an official story was published citing the events that transpired, praising Ghira Belladonna and the Faunus of Menagerie as the ones responsible for stopping the attack, with "a Huntsman and some students" there to lend a hand. Lionheart was honored in the story, said to had died protecting his academy - a story fabricated by Ozpin himself, wishing that his legacy would be remembered in a more positive way, via his lifetime of service, rather than his final moments.