Which council in 1215 issued major reforms including rules on confession and key doctrine statements?

The story behind the answer

In 1215, Pope Innocent III gathered a landmark council in Rome’s Lateran Basilica. Its Canon 21 (Omnis utriusque sexus) required every Christian to confess sins and receive Communion at least once a year at Easter, and it articulated the doctrine that the bread and wine become Christ’s body and blood (transubstantiation). These sweeping measures standardized pastoral care and belief across Latin Christendom.

Beyond confession and doctrine, the council condemned heresies, tightened clerical discipline, ordered regular diocesan synods, urged better education for clergy, and even called a new crusade. Its canons shaped medieval canon law and everyday religious practice for centuries—powerfully influencing how ordinary people related to their parish priest, the sacraments, and the institutional Church.