Pope Gregory issued a list of rules declaring his supreme authority over both church and secular leaders. Gregory declared the pope alone had the power to choose bishops. He even claimed to have the power to remove emperors from the throne.
Go to Milan
King Henry IV wasn't happy about these rules. They were a direct attack on his own power and rights.
The stage was set for a clash of wills between the two men.
Concordat of Worms
The clash began when Henry ignored the popes rules and named his own bishops for the city of Milan, Italy. Pope Gregory then appointed a rival bishop. Next, Henry tried to remove Gregory as pope. Pope Gregory then excommunicated Henry.
Across Europe, members of the clergy and secular rulers took sides.
The power struggle between popes and rulers continued long after Gregory and Henry both died. Eventually, the church and the Holy Roman Empire reached an agreement called the Concordat of Worms. This gave the church the sole authority to appoint bishops and allowed emperors to give fiefs to bishops in order to win their loyalty.