stated motivations for the Zulu invasion of Lourenço Marques and the execution of Ribeiro were the governor's land expansion into Zulu territory, there may have been other reasons unstated in the speech. The commercial downturn accompanying the decline of the slave trade by 1830 effected the Zulu, who may have instead perceived the economic hardship as resulting from Portuguese greed. In addition, Ribeiro's lack of caution in his interactions with the volatile Dingane, who often switched from fighting with or against the Portuguese in the periodic conflicts with other tribes, and the governor's amicable relations with Soshangane, an enemy of the Zulu, were likely contributing factors. Following Ribeiro's death, Nobre, the trader, took over as acting governor. On 21 August 1834, Ribeiro's successor, Dario Rodrigues de Vasconellos, arrived at Lourenço Marques. Two days later, a Zulu representative of Dingane arrived to ask for tribute. By the mid-1830s, the Zulu Kingdom controlled much of the area to the west and south of Delagoa Bay, while Soshangane's Gaza Empire controlled much of the area to the north of Lourenço Marques. In 1835 a group of Boers led by a man named Orich traveled from the Transvaal and attempted to form a settlement on the bay. However, their population was decimated by fever and they soon abandoned the settlement. British and Boer disputes, 1860s–1870s In the 1860s, both the British and Boers made short-lived claims to territory around Deleagoa Bay. On 5 November 1861, Royal Navy Captain Bickford, of the frigate HMS Narcissus, occupied Inhaca Island and Elephant Island, and declared them British territory. Portugal protested this act, and in 1872 the dispute was submitted to the arbitration of Adolphe Thiers, the President of France. Thiers' successor, Patrice de MacMahon, on 24 July 1875 ruled in favor of Portugal, restoring their right to all lands south of Delagoa Bay. Previously, the United Kingdom and Portugal had agreed that a right of pre-emption would be granted to the unsuccessful claimant in case of sale or cession of the bay. Portuguese authority over the Mozambican interior was not established until some time after the MacMahon decision; nominally, the country south of the Manhissa river was ceded to them by the Matshangana chief Umzila in 1861. In honor of the French president's decision, the plaza where the Maputo Railway Station would later be built was renamed Praça MacMahon (Portuguese: "MacMahon Square"). A few years before, in