The island of São Tomé was discovered by Portuguese mariners in 1478 and granted to Portugal's crown prince, together with its sister island, Príncipe (Prince). After the prince's accession to the throne as Joao II, he encouraged settlement of the uninhabited islands to expand the Portuguese presence in this region and promote trade with Africa. The settlers imported slaves from the mainland and a mixed Afro-Euro-pean population emerged who spoke a creole language based on Portuguese and various African languages. In the face of fierce competition from Brazil, sugar was replaced by cocoa as the main crop. In 1975 the Movimiento de Libertaçao de São Tomé e Príncipe or Movement for the Liberation of São Tomé and Príncipe (MLSTP) under the leadership of Manuel Pinto da Costa, led the islands to independence. Under pressure from foreign donors in the late 1980s, the MLSTP government began to liberalize the economy and removed the ban on opposition parties. It was voted out of office in 1990 but returned victorious in 1994 when the interim government failed to cope with economic problems. Miguel Trovoada, who returned from exile to win the presidency in 1991, was reelected in 1996. In July 2001 Fradique de Menezes of the Acçao Democrática Independente or Independent Democratic Action (ADI) won the presidency. In July 2003 his government survived a military coup when Major Fernando "Cobo" Pereira and his rebel soldiers caved in under pressure from the African Union, released their captives and returned to their barracks.