The historical period depicted, the 1920s, was a turbulent period in China, a time of technological and political change, aspects which are all touched on to varying degrees. Indeed, one who knows Chinese history can find starting points for many discussions, including the opening of city walls, the rise of modern machinery, modern technology and modern medicine, the warlords (known as Tuchun — pronounced "doojün"), the western gun boats, opium and the First and Second Opium War, Sun Yat-sen, the Chinese Nationalist and Chinese Communist forces, the influence of Western foreigners, etc. Since this is a book for children, historical events are mainly just touched on rather than described in detail, so as not to slow down the plot.