He came to power after the suspicious death of Zeon Zum Deikun. Degwin was Zeon's chief of staff and claimed that on his deathbed, Zeon, with his dying words, declared Degwin his successor. Degwin Zabi is suspected by most to have a hand in the sudden death of Zeon Deikun, although nothing concrete has ever been uncovered.
Gihren, Degwin's eldest son, initiated a purge of Deikun loyalists, while Degwin Sodo Zabi declared Side 3 colony the Principality of Zeon and himself as Sovereign. He reluctantly initiated a war with the Earth Federation and set his four children up in high ranking positions. Degwin is also consumed by the intrafamilial feuding between his ambitious children, most notably Gihren and his daughter Kycilia. Also, Degwin never recovers from the death of his youngest and most spoiled son, Garma. He falls into a depression since Garma was his favorite child, and leaves most of the day to day operations to Gihren. As a result, Gihren effectively becomes the self-styled "Führer" of Zeon, taking all of his father's remaining power, leaving Degwin as little more than a figurehead.
Although Gihren dismisses his father as a tired old man, Degwin does not hide his disgust for Gihren's ruthlessness. Never having any respect for Gihren's lofty ideals, Degwin once humiliated his son by stating that he would never be Zeon's idea of a Newtype, but only a caricature of Adolf Hitler. He anticipated that as with Hitler, Gihren's own followers would eventually want to kill him.
Although Degwin gives Gihren approval for the Solar Ray laser project, Degwin is genuinely tired of war (after the death of Dozle and brought on mostly by Garma's death) and arranges for a meeting with General Revil to discuss peace negotiations. When the two sides' fleets arrive at the neutral area for discussion, Gihren arranges for the firing of the Solar Ray laser that incinerates Degwin and Revil's respective flagships and much of their accompanying fleets.
|“||May God protect the world from my son. And I can't even imagine what Kycilia might be planning. In the end, Hitler's followers ended up trying to kill him.||”|
—Degwin contemplating the threats, agendas, and fates of his surviving two children.
- In the novelization of Mobile Suit Gundam, Degwin Zabi actually survives the entire war, and is deposed as Zeon leader after the deaths of Gihren and Kycilia and the takeover by Char Aznable.
- In the original 52 episode plan, Degwin would have met with General Revil aboard the White Base. He would then have met Sayla, recognized her as Artesia Som Deikun, and asked for forgiveness, as well as admitting that he had indeed murdered Zeon Zum Deikun.
- While Degwin Zabi does not make many appearances in the Super Robot Wars series, the SRW OE series hinges its interpretation of the One Year War on his survival. Both himself and General Revil meet to conduct peace negotiations like they do in the original anime, and the player is charged with the preventing his and Revil's assassination by defeat of the Zeon forces loyal to Gihren who will use the Solar Ray. This results in a profound change in the plot which involves Gihren going rogue and founding Neo-Zeon to continue the fight.