“I’ve read that during WW1 and again in WW2 many Germans named Mueller changed their names to Miller due to harassment of Germans.”
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There is a major league baseball pitcher (retired now) who was born Sanford Braun. He went into the BB Hall of Fame after a brilliant career with the Dodgers.
You know him as Sandy Koufax.
Then of course there are the “British” royals. Saxe-Coburg-Hesse or whatever it was, became Windsor. Battenberg became Mountbatten. Victoria and her precious “Bertie” Prince Albert I have been told, spoke German when at home.
Many such changes were made Because of WWI.