After establishing his corporation, Oppenheimer quickly shifted his attention from gold back to diamonds. As early as 1910, he had concluded in a memorandum that "the only way to increase the value of diamonds is to make them scarce, that is, to reduce production." He believed that De Beers could bring about such scarcity but only if it expanded its reach beyond the borders of South Africa. He viewed control of the South African mines as a necessary, but not sufficient, condition for an effective diamond monopoly.