According to Cay Van Ash, Rohmer's biographer and former assistant who became the first author to continue the series after Rohmer's death, "Fu Manchu" was a title of honour, which meant "the warlike Manchu". Van Ash speculates that Fu Manchu had been a member of the imperial family of China who had backed the losing side in the Boxer Rebellion. In the early books (1913–1917), Fu Manchu is an agent of the Chinese tong known as the Si-Fan and acts as the mastermind behind a wave of assassinations targeting Western imperialists. In the later books (1931–1959), he has gained control of the Si-Fan, which has been changed from a mere Chinese tong into an international organization under his leadership which, in addition to attempting to take over the world and restore China to its ancient glory (Fu Manchu's main goals right from the beginning), also tries to rout fascist dictators and then halt the spread of Communism, Fu Manchu knowing them both to be major rivals in his plans for world domination. The Si-Fan is largely funded through criminal activities, particularly the drug trade and human trafficking ("white slavery"). Dr. Fu Manchu has extended his already considerable lifespan by use of the elixir of life, a formula that he had spent decades trying to perfect.