Richmal Crompton 
William–the Dictator [EPUB ebook] 

The twentieth Just William volume finds William up to his old tricks, as he sees a fascist “shouting and waving his arms about” and talking about taking over the world in his town, so he thinks that seems like fun so he and his pals call themselves the “Greenshirts” and get themselves some armbands so they can shout and wave their arms and take over the world too.