On this day in 1626 Ethiopian emperor Susenyos I solemnly pledged allegiance to the pope and the Catholic Church.
He did this in the presence of Alfonso Mendes, a Jesuit of Portuguese origin who was at that time the Patriarch of Ethiopia. The Ethiopians had their own Church for centuries prior to this event, the Ethiopian Orthodox Tewahedo Church, which still exists today.
That church currently encompasses around 45 million believers, and is one of the largest Christian confessions apart from Catholicism. However, during the time of Ethiopian emperor Susenyos I, Ethiopia joined the Catholic Church for a time, and recognized the authority of the pope in Rome.
Namely, Portuguese Catholic missionaries managed to convert many Ethiopians, including Emperor Susenyos I from the House of Solomon (which claimed descent from the biblical King Solomon), to their confession. Jesuit missionary Alfonso Mendes became the Patriarch of Ethiopia, while the emperor introduced a number of measures with the goal of converting the Ethiopians to Catholicism.
Many reforms were introduced, including the celebration of Easter according to Roman reckoning. The Saturday Sabbath and circumcision of children were abolished. However, these and similar measures caused a great resistance among the Ethiopian population, which culminated in armed conflict.
Emperor Susenyos I eventually had to give up his attempts to introduce exclusively Roman Rites. Today there are some 600,000 people in Ethiopia who recognize the pope in Rome as their religious leader.