On 10 April 1886, two years after the establishment of German New Guinea, the United Kingdom and Germany agreed to divide the Solomon Islands archipelago into spheres of influence. As a result of this agreement, the islands of Buka, Bougainville, Choiseul, Santa Isabel, Ontong Java, the Shortland Islands, and part of the Florida Islands were placed under a German protectorate ("Schutzgebiet"), which was formally established on 28 October 1886 by the commander of . On 13 December, Kaiser Wilhelm I granted the New Guinea Company a charter to govern the protectorate in accordance with the existing arrangements for German New Guinea. The remainder of the archipelago became the British Solomon Islands Protectorate, which was not formally established until 1893. The present-day boundary between Bougainville and the country of Solomon Islands was established following the Tripartite Convention of 1899, which saw some of the northern islands ceded to the UK in exchange for German control over Western Samoa. The Shortlands, Choiseul, Santa Isabel, and Ontong Java were included in the cession.