During the Clone Wars, he served in the Rarefied Air Cavalry where he fought alongside Anakin Skywalker during the Battle of Virujansi. He greatly admired Skywalker's piloting skills.

Decades later, Dreis joined the Rebel Alliance and was stationed on Yavin IV in command of Red Squadron. When the Empire's Death Star showed up in the Yavin system intent on crushing the Rebel headquarters, it fell to him to lead the daring Rebel counterattack against the massive terror weapon.

The avuncular Dreis and his "boys" in Red Squadron were to keep the battle station's TIE/ln starfighters and turbolaser turrets occupied while Gold Squadron completed the trench run. However, upon the arrival of Darth Vader and Black Squadron, Gold Squadron's Y-wings were destroyed, forcing Dreis to attempt the trench run with his own pilots.

As Dreis's fighter approached the exhaust port, Black Squadron swooped in for another pass. Dreis activated his targeting computer and readied his shot, even as Vader picked off his wingmen. However, this bought Dreis enough time to reach the exhaust port and triumphantly fire his proton torpedoes before pulling out of the trench.

However, victory soon turned to bitter disappointment, as it became clear that Dreis's torpedoes did not enter the exhaust port and merely detonated on the battle station's outer surface. Even worse, Vader had followed him out of the trench and was in hot pursuit.

With time running out, Dreis ordered Luke Skywalker to initiate a final run on the exhaust port, even going so far as to refuse his help against the Imperial fighters. As Luke positioned his flight for the attempt, Dreis was shot down by Darth Vader and crashed into the Death Star's surface. However, his death had not been in vain, as his leadership and sacrifice had given Luke the time he needed to complete his run and ultimately destroy the Death Star.

Ironically, none of the Rebels were aware that the man who had shot down Dreis, Darth Vader, was actually his old comrade Anakin Skywalker—Padmé Amidala's husband, and Luke's father.

Following the Battle of Yavin, Dreis's position as Red Leader would be filled by Commander Narra, who would himself be killed in the Battle of Derra IV.

Luke Skywalker would inherit the Squadron, renaming it Rogue Squadron, and led them until the Battle of Endor, where he was succeeded as Rogue Leader by Wedge Antilles, who renamed the squadron Red Squadron in honor of Dreis and the others who died in the attack on the first Death Star.