Complex sentence: Beginning in the early 1840s, Juba began a series of challenge dances against white rival John Diamond, who advertised that he "delineate (d) the Ethiopian character superior to any other" white "person".
Split into simpler sentences: Beginning in the early 1840s, Juba began a series of dance competitions known as challenge dances. He faced white rival John Diamond, who advertised that he "delineate (d) the Ethiopian character superior to any other" white "person".