Complex sentence: In 1414-1418 the Council of Constance took place, during which, on 6 July 1415, Jan Hus, who was seen as a threat to Christianity by the Church, was burned at the stake.
Split into simpler sentences: In 1414-1418 the Council of Constance took place. During which, on July 6,1415, Jan Hus, who was seen as a threat to Christianity by the Church, was burned at the stake.