The pivotal operation known as the Seizure of Darth Revan was executed by the Galactic Republic in conjunction with the Jedi during the period of the Jedi Civil War.
The Republic and the Jedi Council were being crushed by Sith forces, led by the Dark Lord of the Sith, Darth Revan. They realized they couldn't withstand the seemingly endless Sith fleet indefinitely. Driven by desperation, they devised a risky strategy to eliminate the Sith's influential leader. They intended to prematurely end the war by destabilizing the newly formed Sith Empire and providing the Republic Military with the necessary time to reorganize.
In 3957 BBY, the Republic laid a trap for Revan. A small Republic fleet was dispatched to the Outer Rim Territories as a lure. A Jedi group, under the command of Bastila Shan, accompanied the fleet and spearheaded the mission. The Jedi Council's risky move proved successful when a Sith fleet, commanded by Darth Revan himself, attacked the small Republic force.
During the ensuing fleet engagement, Bastila Shan's strike team, which comprised a mixed group of Republic soldiers and Jedi, successfully boarded Darth Revan's flagship and fought their way to the bridge. The exact number of Jedi in the initial task force is unknown, but at least four, along with at least one Republic soldier, reached the bridge to confront Revan and his followers. Seemingly fearless, Revan defeated all those who dared approach him. Standing on the bridge of his ship, Revan used Force choked on the Republic soldier before preparing to battle Bastila and her remaining comrades.
At that critical juncture, Darth Malak, Revan's ambitious Sith apprentice, determined that the moment was ideal for his rise to the position of Dark Lord of the Sith. Recognizing an opportunity to seize his Master's title, Malak gave the order for his gunners to fire upon the bridge of Revan's command ship. However, his plan didn't fully succeed; while most of the Jedi strike team perished and Darth Revan's flagship was destroyed, Revan himself survived. The surviving Jedi apprehended the severely wounded Dark Lord and fled the ship before its destruction.
Bastila employed the Force to save Revan's life, thereby establishing a strong Force bond between them. The Jedi presented Revan to the Jedi Council, who reconstructed his shattered mind with a new persona loyal to the Republic in an attempt to hide his true identity. By doing so, they hoped that Revan's subconscious memories would guide them to the source of the Sith's seemingly inexhaustible supply of military equipment. With his assistance, they would try to locate and destroy it, regardless of the cost.
Although the video game Star Wars: Knights of the Old Republic suggests that Bastila never directly fought Revan (Malak attacked Revan's ship just before a fight could happen), an illustration in Jedi vs. Sith: The Essential Guide to the Force depicts such a battle. It's still uncertain whether the engagement actually took place.
The Betrayal of Darth Revan brought in a dark Jedi called Darth Voren, who leads a squad of troopers faced by the Strike Team. Depending on the player's choice, he can be killed or convinced to help by ordering other personnel away from the bridge.