During the Yavin blockade in 0 ABY, the 501st Legion retaliated for the destruction of the first Death Star.
A detachment of the 501st emerged from the blockade of Immobilizer 418 cruisers, consisting of one Star Destroyer and two escorting Victory II-class frigates. A number of Rebels had discovered a path through the blockade, and gathered together in a convoy of starships to rip through the blockade with a hyperspace jump.
The pilots of the 501st quickly discovered that a large rebel force was on board several GR-75 medium transports. However, TIE/sa bombers swarmed the transports and quickly took them down. The next main target was the Mon Calamari Star Cruiser. Before they could attack, however, starfighters were being torn to shreds by Corellian Corvettes. Despite this, bombers managed to surround and destroy the Corvettes.
With the odds turned against them, the Rebel fleet chose a daring strategy. They would hyperspace straight through the Imperial Star Destroyer. To deflect any attacks, starfighters were launched against the Imperial forces. They were quickly cut down.
The 501st then launched an assault on the Star Cruiser. The 501st pilots destroyed the heavy turbolasers, clearing the way for the Victory II frigates to barrage the hull. The bombers destroyed the engines and immobilized the starship, stopping the hyperspace jump and leaving the cruiser clear for capture.
The Imperial force then launched a ground assault against the Massassi base. A Sentinel-class landing craft landed on the moon and 501st forces chose to attack a Rebel hangar base inside a Massassi Temple. They secured the fountain and viaduct. Fighting through a heavy Rebel force, including AAC-1 speeder tanks, they next captured the reflecting pool.
The Rebel forces, who had been caught off guard by the sudden attack, managed to regroup and begin a counterattack. Closing a blast door over the hanger behind them, a massive force of infantry and armor attacked the reflecting pool. However, the Imperials, despite high casualties, managed to stop the attack in its tracks.
Before they could attack the main temple, they would have to break through the door. A squad of Imperial engineers deployed a bomb to the hangar door, blowing it open. The Imperials then stormed the temple and went into an all out brawl with the remaining rebels. Using this as a distraction, a squad of stormtroopers entered a small command room and killed the Bothan High Command.
After killing the High Command, the 501st Legion evacuated back to the Imperial fleet in orbit to move to other battlefronts.
This is another presentation of the events prior to the Evacuation of Yavin from the 2005 video game Star Wars: Battlefront II.