Wahlen was one the many admirals who was named to serve under Reinhard von Lohengramm. His first major battle was the Battle of Amlitzer, where he ambushed the Eighth fleet of the Free Planets Alliance , effectively wiping it out. During the Lippstadt Rebellion, he served alongside Siegrfied Kircheis and Cornelius Lutz in the battle of Kifeuser.
Wahlen also participated in the Battle of Vermilion against the Free Planets Alliance.
Later, Wahlen was Assigned by Kaiser Rheinhard to head the assault on Earth. During the mission, he was almost assassinated by a terran fanatic in which he was stabbed in the left arm with a poisoned knife, and fell into a coma for a few days, during that time, his arm had to be amputated in order to save his life. after the assault, he met up with Julian Mintz, Louis Mashengo, and Oliver Poplan, and fulfilled Julian's wish to go to Odin.
He later took part in the second battle of Rantemario, where his prosthetic arm was blown off from an explosion as a result from a direct hit from Ruenthal's fleet.
Wahlen would re-appear in the Retriever arc of Spiral Labyrinth, where he assissted both Reinhard and Kirchies on thier mission into alliance territory.
Wahlen is known to have a least one child, a son, whose name is not known.