With the exception of 1927, he was Der Stürmers sole regular cartoonist under the pen-name of "Fips" until February 2, 1945, when the last edition of Der Stürmer appeared, drawing thousands of antisemitic caricatures.
At the beginning of World War II, Rupprecht served in the Kriegsmarine, but was released from service because of his value to wartime Nazi propaganda.