Best answer: by disagreeing with the pope
There had been much struggle between Pope Boniface VIII and the French king, Philip IV, over control of the church in France. Philip actually sent men to rough up Boniface during that time. After Boniface's death and then a papacy of less than a year by Benedict XI, pressure from France resulted in the electing of a French cardinal as Pope Clement V, in 1305. Clement moved the office of the papacy from Rome to Avignon, which was in Holy Roman Empire territory but near the border of France. The papal offices stayed in Avignon, under French domination, from 1309 to 1376, with seven popes total governing the church from there.
Gregory XI, the last French pope, returned the offices of the papacy to Rome in 1377. When Gregory XI died in 1378, an Italian again was elected to be pope – Urban VI. But very quickly many cardinals (especially the French) regretted the election of Urban VI. The French cardinals put forth their own rival pope, Clement VII, later in 1378. This began the Great Schism, also known as the Western Schism or Papal Schism. There were competing popes claiming the authority of that office and the allegiance of Catholics in Europe. The split in the papacy lasted till 1417.
