Miguel joins ZAFT in order to earn the doctor's fee for his younger brother who was sick; known as the "Magic Bullet Of Dusk" because he usually pilots a customized GINN that is orange coloured, just like the colour of dusk, and with the high mobility of the custom GINN his combat style specializes in delivering deadly blows; a ZAFT ace under the command of Rau Le Creuset. Miguel is shown as a head-strong and somewhat arrogant individual, normally underestimating his Natural opponents.
Miguel participates in the transferring of the asteroid base Nova to the PLANTs, though he thought it wouldn't be fun. However, he engages Mu La Flaga during an Earth Forces raid. In January C.E. 71, the Nazca-class Vesalius under the command of Rau Le Creuset is sent out to investigate the mysterious destruction of ZAFT supply bases. While on patrol, Miguel discovers the culprit behind the attacks: Serpent Tail mercenary Gai Murakumo. Miguel's GINN is damaged in combat with Gai's custom GINN, forcing him to switch over to a standard GINN for the attack on Heliopolis on January 25.
During the attack on Heliopolis in Gundam SEED, Miguel tries to capture the GAT-X105 Strike after hearing from Athrun Zala that Rusty Mackenzie - the ZAFT pilot who was supposed to take it - has been killed, and that the Strike is being piloted by an Earth Alliance soldier (Murrue Ramius). However, Athrun fails to mention that Kira Yamato, his childhood friend is also in the cockpit, and that Kira is a Coordinator like they are. Miguel tells Athrun to get the GAT-X303 Aegis out of Heliopolis before it gets damaged, and then tries to take on the Strike himself. Murrue is no match for Miguel, and seeing that his friends Sai Argyle, Kuzzey Buskirk, Miriallia Haw, and Tolle Koenig are in the vicinity of this battle, Kira takes control of Strike and fights back, ultimately forcing Miguel to retreat after disabling the ZAFT pilot's GINN. Miguel quickly pulled the self-destruct trigger and got out of his GINN before it exploded.
Thinking that a Natural was piloting the Strike, Miguel is humiliated by his defeat and vows to get revenge. Miguel is ultimately killed when Kira slices his GINN and him in half at the torso with the Strike's Schwert Gewehr (the same weapon that he would use to kill Nicol Amalfi in a later battle); Miguel has the dubious distinction of being the first person killed in action by Kira Yamato.
