Extensive research was done for the cultures, particularly areas such as costuming, technology, and music, to develop an alternate world which merges aspects of WWII Nazi and Imperial Japanese cultures with the cultural progress of mid-1950s America. Although the series is set in 1962, the use of the 1950s for many touchstones suggests the cultural stagnation that would have occurred under totalitarian occupation.
SS Headquarters in New York appears to be in the same location as the real headquarters of the United Nations.
Real historical figure Reinhard Heydrich plays an important role in the first two seasons. While the real Heydrich was assassinated by the Czech resistance in 1942, he survives in the reality of the series. Curiously, Heydrich's survival is a recurrent theme in other alternate reality works, such as Robert Harris' Fatherland and Harry Turtledove's In Presence of Mine Enemies. Most historians agree that, had Heydrich lived in a victorious Third Reich, his temper, personality, ambition, extremism and age (he was younger than Hitler) could have made him clash with his superiors, and possibly Hitler himself.
John Smith carries the rank of Obergruppenführer ("senior group leader"), while his superior Reinhard Heydrich has the similar-sounding rank of Oberst-Gruppenführer ("supreme group leader" or "colonel group leader"). During WWII, these were the two highest SS commissioned ranks, with Oberst-Gruppenführer reporting directly to the Reichsführer-SS, Heinrich Himmler. The rank of Obergruppenfuhrer is the equivalent in U.S. Army ranks to Lieutenant General, three stars.
Inspector Kido is frequently addressed in English by his Japanese title, tai, as in Kido tai, i.e. Inspector Kido. This is a play on the Japanese word for riot police, kidotai.