Here, as on the west coast, disintegration and retrogression followed, for as the American traffic lessened, the Arabian traffic increased. When, therefore, Stanley opened the Congo valley to modern knowledge, Leopold II of Belgium conceived the idea of founding here a free international state which was to bring civilization to the heart of Africa. Consequently there was formed in 1878 an international committee to study the region. Stanley was finally commissioned to inquire as to the best way of introducing European trade and culture. "I am charged," he said, "to open and keep open, if possible, all such districts and countries as I may explore, for the benefit of the commercial world. The mission is supported by a philanthropic society, which numbers nobleminded men of several nations. It is not a religious society, but my instructions are entirely of that spirit. No violence must be used, and wherever rejected, the mission must withdraw to seek another field."[28] The Bula Matadi or Stone Breaker, as the natives called Stanley, threw himself energetically into the work and had by 1881 built a road past the falls to the plateau, where thousands of miles of river navigation were thus opened. Stations were established, and by 1884 Stanley returned armed with four hundred and fifty "treaties" with the native chiefs, and the new "State" appealed to the world for recognition. The United States first recognized the "Congo Free State," which was at last made a sovereign power under international guarantees by the Congress of Berlin in the year 1885, and Leopold II was chosen its king. The state had an area of about nine hundred thousand square miles, with a population of about thirty million. One of the first tasks before the new state was to check the Arab slave traders. The Arabs had hitherto acted as traders and middlemen along the upper Congo, and when the English and Congo state overthrew Mzidi, the reigning king in the Kantanga country, a general revolt of the Arabs and mulattoes took place. For a time, 1892-93, the whites were driven out, but in a year or two the Arabs and their allies were subdued. Humanity and commerce, however, did not replace the Arab slave traders. Rather European greed and serfdom were substituted. The land was confiscated by the state and farmed out to private Belgian corporations. The wilder cannibal tribes were formed into a militia to prey on the industrious, who were taxed with specific amounts of ivory and rubber, and scourged and mutilated if they failed to pay. Harris declares that King Leopold's regime meant the death of twelve million natives.