By the 1850s, interest in African exploration had become an international race. Explorers like David Livingstone, Henry M. Stanley, and Heinrich Barth became national heroes, and the stakes were high. A public debate between Richard Burton and John H. Speke over the source of the Nile led to the suspected suicide of Speke, who was later proven correct. Explorers’ travels also helped pave the way for European conquest, but the explorers themselves had little to no power in Africa for much of the century. They were deeply dependent on the African men they hired and the assistance of African kings and rulers, who were often interested in acquiring new allies and new markets.