The party was accused of endorsing systems of forced labour. In 1930 they sent "contract migrant laborers", under conditions tantamount to slavery, to Spanish colonists on Fernando Pó in Spanish Guinea (now Bioko in Equatorial Guinea). This led to an investigation by the League of Nations, a five-year U.S. and British boycott of Liberia followed by the resignation of President Charles D. B. King. Despite this dispute, the West generally considered the True Whig Party as a stabilizing, unthreatening force in the period after. The US and Britain later invested extensively in the nation under William Tubman's long period of rule (1944–1971).