The Galactic Republic's Grand Army of the Republic—assisted by the Jedi Order—and the Confederacy of Independent Systems waged a battle on the planet Hypori in 22 BBY as part of the Clone Wars. The Republic's 442nd Siege Battalion and 212th Attack Battalion were deployed in the destructive battle, though the Republic was ultimately defeated by the Kaleesh cyborg warlord General Grievous and his Separatist Droid Army.
The defense of Dantooine (pictured) was a Republic victory that led into the battle of Hypori.
The onset of the Clone Wars in 22 BBY was sparked by the First Battle of Geonosis, where the Galactic Republic had seen a first victory against the Confederacy of Independent Systems that had been costly due to the loss of many Jedi. The trend of success that began with the Battle of Geonosis continued during the Battle of Christophsis, and the defense of Dantooine, which was still ongoing by the time the battle of Hypori began, also met the Republic's forces with victory.
In 22 BBY, following the battles of Christophsis and Dantooine, the Galactic Republic and Jedi Order were involved in a battle on the Outer Rim world Hypori against the Confederacy of Independent Systems. The Grand Army of the Republic's 442nd Siege Battalion and the 212th Attack Battalion fought in the battle. During the engagement, a group of Jedi Knights were taken by surprise and an Acclamator-class cruiser crashed into Hypori. The battle ultimately ended with a slaughter of the Republic forces, and the death of a number of clone troopers and Jedi at the hands of the Kaleesh cyborg warlord and Supreme Martial Commander of the Separatist Droid Armies General Grievous. At least one participating B1-series battle droid was destroyed in the battle as well.
Kenobi hoped that volunteering his troops for the Battle of Abrion Bridge (pictured) would revitalize their morale following their loss on Hypori.
The events of the battle on Hypori led to a wave of fear and demoralization among Republic forces, much of which concerned the threat of Grievous, as well as the rapid expansion of the war. This fear—alongside a newfound sense of responsibility from the newly anointed Jedi General Obi-Wan Kenobi and exhaustion caused by the Battle of Christophsis—lingered as the Jedi Master prepared for the oncoming Battle of Abrion Bridge. In order to encourage his forces, Kenobi attempted to live up to his newfound leadership role and volunteered the 212th Attack Battalion to lead the assault on Abrion Bridge.
When an engineering team led by Commander Orson Callan Krennic of the Galactic Empire moved into a former Techno Union droid factory located on Hypori to work on weapons design and production for a secret mobile battle station during the Imperial Era, the hulk of the Acclamator-class cruiser stood as a grim memorial of the battle. Around 0 BBY, Kenobi thought about the aftermath of the battle of Hypori, recounting its disastrous course as well as the manner in which the engagement had demoralized Republic forces.
The battle of Hypori was first mentioned in the current Star Wars canon in the 2016 novel Catalyst: A Rogue One Novel, written by James Luceno. It later went on to make its first appearance in the third issue of the comic miniseries Star Wars: Obi-Wan, which was written by Christopher Cantwell, pencilled by Alessandro Miracolo, and published by Marvel Comics on July 27, 2022. Prior to the issue's release, the battle was first pictured in a preview for it published on StarWars.com on July 20.
The Clone Wars-era battle on Hypori was originally first depicted in the Star Wars Legends continuity in Chapter 20 of the animated microseries Star Wars: Clone Wars, which aired on April 8, 2004 on Cartoon Network. It was first identified as the "Battle of Hypori" in the Legends continuity in Star Wars Fandex Deluxe Edition, a 2008 fold-out reference guide written by Christopher Cerasi. The canon novel Brotherhood, written by Mike Chen and published on May 10, 2022, includes an indirect reference to the Legends Battle of Hypori regarding Jedi Master Ki-Adi-Mundi healing from scars he sustained during a recent encounter with Greivous. Chen later revealed it was part of his aim to work aspects of the Clone Wars animated series into his book.