Following the overthrow of his uncle Pedro Nkanga a Mvemba, King Diogo, the grandson of King Afonso I of Kongo, assumed the throne. In Sao Salvador, his uncle was forced to seek safety in a church.
He severed relations with the Portuguese as part of his purging of the palace. He viewed their interference in the kingdom’s affairs as a challenge to his authority. He expelled all 70 Portuguese citizens from his realm in 1555. According to Dbpedia, this was confirmed in a court investigation of Pedro Nkanga a Mvemba’s attempt to depose him in 1550.
According to historical records, the former monarch planned his scheme while seeking safety in the chapel. With the help of some Kongolese lords who swore fealty to him, the plot was organized.
Jorge Afonso, his magistrate and purveyor, was urged to conduct the inquest by Diogo. He obtained testimony from Kongolese lords who had sworn allegiance to the conspirators and Diogo as well as those who asserted their neutrality inside the kingdom.
The task of ridding the realm of conspirators—many of them were in his court and loyal to the previous king—was more important for the king. If he quickly cut off the conspirators, he ran the risk of making a dozen enemies. On the other hand, any delay increased the challenge to his authority.
He replaced the former king’s supporters gradually and swiftly in an intentional but purposeful way so he wouldn’t hesitate to remove them. After putting his critics on the defensive, Diogo focused on reducing the Portuguese’s influence over Kongo’s domestic affairs.
He reportedly had issues with the Tomistas, as the Portuguese immigrants of Sao Tome were known. According to a contract between Kongo and Portugal, the Portuguese were only allowed to trade for slaves within Kongo’s area. In other words, Diogo either gave the Portuguese slaves or made people to sell them. However, the Portuguese deviated from the agreement.
The arrangement was actually broken, according to Just World News, because of the Tomista traders’ custom of sailing upriver to the Malebo Pool to buy slaves from BaTeke merchants who grew more interested in European products than the nzimbu shells the manikongo supplied them. Infuriated by this infringement of the agreement, King Diogo severed ties in 1555.
Diogo had introduced a competing religion before this to the Catholic Church. Soon after the first Portuguese explorers reached the Kingdom of Kongo’s coasts in 1483, the Catholic Church had already established there. Diogo, however, provided room for Jesuit Catholic missionaries in 1548 while he was in power. There were rumors that the secular and Capuchin priests were against it. In 1555, Diogo changed his allegiance from the Jesuits, leading him to expel them from the area after they demanded that he give up everything he possessed.
He introduced Franciscan missionaries to the kingdom in 1557 and attributed to their beliefs. Until his passing in 1561, he remained devoted to them.