Concurrent with these three acts, the Belgian Anti-Slavery Society raised another, and quite distinct, volunteer corps for similar work, but restricted to the neighbourhood of Lake Tanganyika. In addition, about this period the same Society despatched to Congoland, in rapid succession, three expeditions of a missionary and civilising character. In such circumstances, collisions between the Belgians and Arabs were inevitable. During the first few years of the existence of the Congo Free State these collisions occurred chiefly on the Upper Congo and its tributaries, the currents of the interior slave trade, particularly those from the eastern and southern provinces, being checked by fixed military posts and flying columns. For two years—from 1892 to 1894—a continuous campaign was in progress, having for its object the interception of the slave caravans accustomed to come from the south and east, which was entirely successful. In the vast territory known by the name of Lualuba-Kassai, at a time when the resources of the State were unequal to the expense of maintaining a line of posts, it was usual, up to so recently as 1902, on the appearance of a gang of slave-dealers to despatch a detachment of troops from Lusambo or Luluabourg to intercept them. Many engagements were thus brought about between the State volunteers and the slave-dealers. Now military posts are established on all the principal roads formerly used by the slave-traders, and the barrier is complete. In the north, Commandant Chaltin struck a damaging blow to the Dervishes in February, 1897. After traversing with his force the whole of the Uelle territory, he encountered the Dervishes at Redjaf on the Nile. The place was strongly held by four thousand soldiers, more than half of whom were armed with modern rifles. A severe battle ensued, lasting nearly all day. Victory lay with the Belgians, the Dervishes being forced to evacuate Redjaf. They accepted their beating badly, making several attempts to retake the place, but without success. Thus we have seen that it was in the districts of the Lower Congo that the slave trade was first stamped out; that it was next eradicated from the Middle Congo; and finally extinguished on the Upper Congo, where Belgian bravery and military skill succeeded in effectually crushing the last vestige of Arab power. [Sidenote: Negro Advancement.] The Negro was quick to respond to the revivifying influence of security for life and property, and his rapid progress in civilisation may be said to date from the day when this essential primary condition was established. From a report to King Leopold made by Baron Van Eetvelde, Secretary of State for the Independent State of the Congo, the following passage is extracted: