Missionaries began visiting the Solomons in the mid-19th century. They made little progress at first, because "blackbirding" (the often brutal recruitment of laborers for the sugar plantations in Queensland and Fiji) led to a series of reprisals and massacres. The evils of the labor trade prompted the United Kingdom to declare a protectorate over the southern Solomons in June 1893. This was the basis of the British Solomon Islands Protectorate . In 1898 and 1899, more outlying islands were added to the protectorate;in 1900 the remainder of the archipelago, an area previously under German jurisdiction, was transferred to British administration apart from the islands of Buka and Bougainville which remained under German administration as part of German New Guinea (until they were occupied by Australia in 1914, after the commencement of the First World War). Traditional trade and social intercourse between the western Solomon Islands of Mono and Alu (the Shortlands) and the traditional societies in the south of Bougainville, however, continued without hindrance. Under the protectorate, missionaries settled in the Solomons, converting most of the population to Christianity. In the early 20th century, several British and Australian firms began large-scale coconut planting. Economic growth was slow, however, and the islanders benefited little.