 Luther’s position on indulgences, and his challenge to the Pope, had now begun to draw the attention of higher authorities in the Church, and in 1518 he was summoned to Augsburg to meet with the papal legate Cardinal Tommaso de Vio, known as Cajetan, who was investigating the matter. He tried to get Luther to recant, but he refused to back down in any way. In 1519, Luther travelled to Leipzig for another disputation, this time with Johann Eck, a theologian who had earlier criticised his Ninety-Five Theses. The confrontation was a highly charged affair, also conducted in printed pamphlets and associated satirical texts written by supporters, in which Luther again vehemently defended his ground. Eck then travelled to Rome to make his case, hence contributing to the papal decision to issue the bull Exsurge Domine on 15 June 1520, which threatened to excommunicate this troublesome opponent.