Numerous independent entrepreneurs expanded the Empire, such as Stamford Raffles of the East India Company who founded the port of Singapore in 1819. Businessmen eager to sell Indian opium in the vast China market led to the Opium War (1839–1842) and the establishment of British colonies at Hong Kong. One adventurer, James Brooke, set himself up as the Rajah of the Kingdom of Sarawak in North Borneo in 1842; his realm joined the Empire in 1888. Cecil Rhodes set up an economic empire of diamonds in South Africa that proved highly profitable. There were great riches in gold and diamonds but this venture led to expensive wars with the Dutch settlers known as Boers.