"Heinz Bruckner" was the alias of a Rutan spy disguised as a "highly decorated" human Nazi officer who was looking for the world engine weapon the Warsong to claim for the Rutans. The Twelfth Doctor speculated that the real Heinz had been dead and impersonated by the Rutan for a while.
In 1941, Bruckner orchestrated artillery strikes and bombings to try and locate and activate the Warsong, which activated in the presence of aggressive technology. The Twelfth Doctor believed that Bruckner had a "vague idea" of the weapon and used the attacks to triangulate responses from the Warsong. After the arrival of the TARDIS, the temporal motors of the TARDIS began to cause the Warsong to stir even faster. Bruckner framed the Twelfth Doctor and Clara Oswald as spies and took Clara as a prisoner. He used the chronal energy that lay inside Clara to pinpoint the location of the Warsong and triggered it. He used an activation device to conduct and guide the weapon as it turned the nearby resources, and eventually, all of Earth, into a weapon. Before this was done, however, the Doctor and Field Marshal Rommel broke through the defences of the Warsong, and the Doctor used a Sontaran osmic projector to send Bruckner's control device for the Warsong through time. Rommel then threw Bruckner into the Warsong, killing him. (COMIC: The Instruments of War)