Koller was born in Glonn in Bavaria. An exemplary officer, he graduated valedictorian at the Air War Academy. He was the Chief of Staff for Hugo Sperrle during the Blitz. For Operation Sea Lion, the planned invasion of the United Kingdom by the Wehrmacht, Oberstleutnant Koller was to serve as the Operations Officer of Luftflotte 3, in coordination with the German 9th Army.
Although Koller supported Göring against the Heer and the Kriegsmarine, he was one of Göring's harshest critics, writing that "one had the feeling that he [Göring] had no interest in bringing about an atmosphere of smooth cooperation, that he was almost afraid that this would lead to the establishment of a phalanx against himself. Koller became the Chef der Luftwaffenführungsstabes ("Chief of the Luftwaffe Operations Staff") in October 1943, which essentially made him as assistant to the General Staff.
On the morning of 20 April 1945, when Berlin came under Soviet artillery fire for the first time, he informed Hitler that the shells hitting the city were not from long-range cannons, but from a battery in Marzahn - a suburb which is (as Hitler noted with rage) only 12 kilometers away from Berlin's center. After the war, Koller spent several years in British captivity, was released at 1947 and returned to Bavaria.
In 1949 he published his wartime shorthand diary as the memoir Der letzte Monat (The Last Month, Mannheim), which provided information about Hitler's last days during the Battle of Berlin. Koller also served as the chairman of the Verband Deutscher Soldaten in Bayern. He died in his hometown of Glonn in 1951.
In the Parodies
Who is cooler than Koller? He’s the most laid-back general in the Downfall. He had dialled, probably by mistake, Hitler’s phone number and then having no choice, told his leader about Soviet artillery established only a few kilometers from Berlin (7:30; Downfall “Extended” version). He’s reporting it very calmly, supposedly thinking in his mind “Artillery or nukes, who cares?”. Hitler becomes angry hearing the bad news. Koller just listens to all his complaints, waiting for a moment when the Führer will overreact and bang the receiver down, so that all those misunderstandings will be finally cut off. Koller’s example proves that chill-out peeps existed in the Third Reich.
Koller probably has problems formulating thoughts, though not to the level of Günsche's dim-wittiness, as evidenced by most of parodies involving him in which his reports (sometimes even thoughts) have to be passed on paper to him by a subordinate, so that he has something to say to Hitler.
Koller seems to employed at multiple companies in various different helpdesk functions, since he is frequently the person picking up the phone when Hitler calls for someone. Examples are pest control, Windows 1945 expert and Santa Claus.
Koller also happens to be one of the most edited-out characters among the Hitler parodies. The scene in which Koller calls the Führer has been routinely edited by Untergangers to have Hitler call all sorts of different people to vent his frustrations. In the Downfall parody universe, Koller is well aware of the situation and becomes calmly pissed off at Hitler for allowing this to happen, resulting in Koller "bastardizing" the YouTube webpage display.
- Koller is visible in the Hitler plans scene, when Keitel talks to Hitler. Later he is no longer in the room.
- In a deleted scene, available in the Premium Edition, Hitler orders Koller to mobilize the remaining air force to support Steiner's attack. He also threatens Koller with death sentence if he defects. Koller complies and leaves. This exchange occurred prior to Joseph Goebbels's opening line.
- Some Untergangers call him "Kohler".
- A gag is that Koller sounds like "caller" or "hello", as indicated by the many phone scene parodies.
- In HRP's The Assassination of Hitler, he actually had one of the best chances of becoming Fuhrer after Hitler died, having complete control of the communication systems in the Reich. Unfortunately, he failed all the same because his cronies were useless idiots who'd do anything for him.