Simony: the sin of buying or selling church office. Named after Simon Magus.

Investiture Controversy: whether or not secular rulers can appoint ("invest") bishops and priests.

800: Pope Leo III crowns Charlemagne as Western Roman Emperor.

827: Einhard (Charlemagne’s biographer) sends his servants to Rome to steal some holy relics.

909: Foundation of monastery at Cluny. By 1000, there are 30 Cluniac monasteries; by 1100, there are 600.

c.975: Peace of God movement begins in France.

1046: Synod of Sutri. Church reformers, in alliance with the German emperor Henry III, pass legislation against simony and against clerical marriage.

1059: Pope Nicholas II issues decree on election reform. Hereafter, popes are to be elected by the College of Cardinals, free from lay interference.

1073-1085: Pope Gregory VII.

1075 issues Dictatus Papae.

1077 forces emperor Henry IV to do penance at Canossa.

1088-1099: Pope Urban II.

1095 proclaims first Crusade in speech at Clermont.

1122: Concordat of Worms ends investiture controversy between popes and emperors.

1215: Fourth Lateran Council, convened by Pope Innocent III to legislate on matters of faith and on church discipline.