The Doctor was the main scientist for the Millennium Organization, a true scientist and lunatic whose mind handled capably topics as wild and varied as the development of the vampirization surgeries, microchips designed to monitor accurately every part of the vampire they were implanted into, to the creation of Schrodinger, a quantum-reality based cat-boy. The Doctor, habitually seen with a set of multiadjustable lenses, was first seen in the Warsaw Order 666 camp, striving to understand the mechanics behind the creation of vampires. He eventually became a staple for all Millennium reunions, one of the few who could truly understand the Major and his cause.
Despite all his genius, in the onset of the vampire production process, and despite the increased influx of Russian war prisoners as living guinea pigs, he could initially create ghouls, rather than vampires, and his original ghouls lasted less than four hours before their metabolisms became unstable. The vast majority of those exposed to his surgeries and serums died. Nevertheless, the Major was delighted with the product, and while admitting its flaws, could imagine its possible warfare applications with ease. He was last seen exiting the compound's officer dining room with the Major to allow the Captain to do free combat with Walter; during this dinner he expressed intense admiration and curiosity about the monster codenamed "She" or THE SHI, and desperately asked the Major what it was. Instead of outright answering, the Major gave him an indirect answer and later called Alucard in his then-current incarnation the origin, foreshadowing the roles of both in the future war.
He can be considered the essential responsible for the creation of the Millennium Army of a thousand vampires. Residing in the Millennium airship, the Hindenburg II, he was seen more often than not habitually using his remote or control panel to various effects, such as incinerating failed Millennium officers, blowing up Alucard's gun or activating a series of traps within the airship itself. While more normal (as normal as he could be) than his fellow Millennium officers, he had not aged for over fifty years when seen in the London assault, which leads to the conclusion he either used his own process within him or had his mind shunted into a machine body, much like the Major himself.
He used this vampirization process upon former Hellsing trashman Walter C. Dornez, though time constraints led him to execute a poor, flawed surgery. The result of this, predictably, was an unstable vampire who ended up rejuvenating too much, to his mid-teens. The Doctor, choosing to remain in the burning, downed airship, was confronted in his laboratory by Walter, who accused him of being a pathetic scientist, and that all he had created was good for nothing, including himself in that statement. The Doctor started ranting on how his research would eventually lead him to surpass Alucard, but Walter remained skeptic. The Doctor attempted to incinerate him, only for Walter to cut off his arm and leg. Falling, the Doctor pulled a curtain behind which was the original source of vampire material for the Millennium Group-the dead remains of Mina Harker, used and exploited for that purpose from her apparent death. Walter realized this only confirmed his theories; all the Doctor had done was to bootleg cheap copies of Alucard; he took solace in humiliating the Doctor further before wreckage of the zeppelin and the flames killed them both.
Oddly enough, he has been mentioned as having a slew of unusual talents, such as cooking. He was even complimented by his sauerkrat and other cuisine pieces by the Major when his dinner was interrupted by a young Walter in the Millennium Projekt compound in Warsaw, 1944.