The man the high school is named after, Fritz Julius Kuhn, was the leader of the German-American Bund (German-Americans loyal to Adolf Hitler and the Nazi Party) prior to World War II. He became a nationalized U.S. citizen in 1934, but his citizenship was revoked in 1943 and he was deported to Germany in 1945.
General Hidehisa Onoda is a reference to Hiro Onoda, a real Japanese officer of the Imperial Army who famously kept fighting in the Philippines for 29 years, refusing to believe the news of Japan's surrender and dismissing everything -even letters from his own family- as enemy propaganda. He finally surrendered in 1974 following a direct order from his superior officer, who had been tracked down. General Onoda is the right age for the time period and, in the world of The Man in the High Castle, a committed officer such as the real Onoda could have risen through the ranks very quickly in a victorious Japan.
The Bellamy salute is a palm-out salute described by Francis Bellamy, the author of the American Pledge of Allegiance, as the gesture which was to accompany the pledge. During the period when it was used with the Pledge of Allegiance, it was sometimes known as the "flag salute". Both the Pledge and its salute originated in 1892. Later, during the 1920s and 1930s, Italian fascists and Nazis adopted a salute which was very similar, and which was derived from the Roman salute, a gesture that was popularly (albeit erroneously) believed to have been used in ancient Rome. This resulted in controversy over the use of the Bellamy salute in the United States. It was officially replaced by the hand-over-heart salute when Congress amended the Flag Code on December 22, 1942.
The Kempeitai were the military police of the Japanese Imperial Army. Literally translated, the name means "Law Soldier Regiment." Westerners of 1930's generally called them "gendarme" In Western countries, "military police" are associated in the public mind with keeping order among off-duty personnel, such as arresting drunken servicemen. The Kempeitai had a much more sinister role, especially during World War II. There was no right of habeas corpus and suspects were considered guilty when arrested. The Kempeitai also enjoyed almost complete autonomy and freedom from restraint.
When Frank confronts Albert about his job in the listening room, he calls him a "Pon." This is apparently slang and short for Nippon which means Japan. "Nip" was a pejorative used during World War II.