Science fiction writer William F. Wu said that American adventure, crime, and detective pulp magazines in the 1930s had many Yellow Peril characters, loosely based on Fu Manchu; although "most Peril characters were of Chinese descent", the geopolitics of the time led white people to see Japan as a threat to the United States. In "The Yellow Peril: Chinese Americans in American fiction, 1850–1940" (1982), Wu said that fear of Asians dates from the European Middle Ages, from the 13th-century Mongol invasion of Europe. Most Europeans had never seen an Asian man or woman, and the great differences in language, custom, and physique accounted for European paranoia about the nonwhite peoples from the Eastern world.