When the SDF-1 crash landed on Macross Island, many of Earth's brightest minds were pulled together to try and piece together the enemy tech. (Macross Saga: "Boobytrap") One of the leaders in this was Osmund, who appeared to be German. (Robotech: Invasion Part 4)
Osmund survived the destruction of much of the Earth, most likely placing him onboard the SDF-1 during the conflict, and went on to work for the Earth forces after all. In the year 2039, he was noted as one of the Earth Reclamation Force's best scientists. (Robotech: Invasion Part 4)
By 2042, he had built up a fortress near Graystone, where he conducted experiments on breaking the Invid Hive's shield, based on what he had seen at the hive in Paraguay. He built a secret weapon which held this cause, named "the Destructor," which he believed would lead to him being the man to personally liberate the Earth.
On 29 November, Locke, Guppy, and Arturo reached his confines on their way to Point L. He refused to let them pass, worrying that they would disrupt his weapon tests. Locke attempted to find another way across the fortress instead, while his partners distracted Osmund. Osmund snuck into his base and opened the doors from the inside, angering Osmund, who proclaimed that his weapon was highly important and that the liberation of the Earth from the Invid was "his burden to bear." The trio, convinced he was insane, ignored him and kept on their travels. Osmund swore that the group would pay for their insolence.
The Doctor later arrived in Haven City to attempt to fend off the Invid with his secret weapon. He attacked the forces in his Destabilizer Tank and was able to fend them off for a while, before being grabbed out of his tank and flung away by Resa.
He hid his ultimate weapon, the H-109P Destabilizer, near the area. Resistance fighters Maria Allentes, Anna, Vera, and Tasha Dixon successfully retook the weapon from this hiding place. Furious at the group for stealing his glory, he attempted to fight them. Upon loosing the conflict, he blew his Tank up, blocking the entrance in the nearby caves to Reflex Point, while exclaiming "If I cannot have it, no one can!" (Robotech: Invasion)