According to Wikipedia (https://en.wikipedia.org/wiki/Flag_of_Germany), the flag of Germany was the same for nearly 15 years following WWI. In 1935 following the rise of Hitler, the flag changed to the well-known red background with the swastika. How did the international community react to such a radical redesign of the country's symbol, particularly given that it included a heretofore (in the West at least) unique symbol?
There is unfortunately very little to say about the whole Swastika Flag buisness since people already associated the flag with the Nazis and after 1933 the flags were used alongsite each other. I have written about this previously here and could not find anything about a specific international reaction.