In 1894, King Leopold signed a treaty with Great Britain which conceded a strip of land on the Congo Free State's eastern border in exchange for the Lado Enclave, which provided access to the navigable Nile and extended the Free State's sphere of influence northwards into Sudan. After rubber profits soared in 1895, Leopold ordered the organization of an expedition into the Lado Enclave, which had been overrun by Mahdist rebels since the outbreak of the Mahdist War in 1881. The expedition was composed of two columns: the first, under Belgian war hero Baron Dhanis, consisted of a sizable force, numbering around 3,000, and was to strike north through the jungle and attack the rebels at their base at Rejaf. The second, a much smaller force of 800, was led by Louis-Napoléon Chaltin and took the main road towards Rejaf. Both expeditions set out in December 1896.