Throughout the middle ages, and especially in the 12th-13th centuries, there was a power struggle between ruling monarchs and the Popes. Among temporal rulers, the Holy Roman Emperors often came into direct conflict with the papacy.
Frederick I (1122-1190) was a Holy Roman Emperor that hailed from the Hohenstaufen family and was very focused on ending political decentralization within his territories. He sought to bring the various Lombard kingdoms under his control, as well as their resources. The plunder he got from these towns would ensure a strong hold over his own German lands. Pope Alexander III (c. 1100-1181) was concerned with Frederick’s advances into Italy because he might try to interfere with Church matters, so he formed an alliance with the Lombard league of cities. In response, Frederick burned down the city of Milan. Eventually, the Lombard forces were able to drive Frederick back, and there was a reconciliation between him and the Pope, but this was not the end of tensions between the Holy Roman Emperors and the papacy.
After the death of Henry VI (1165-1197), Frederick I’s successor, there were two candidates for the title of holy Roman Emperor put forward by the rival Hohenstaufen and Welf families. The Hohenstaufens already had the kingdom of Sicily under their control, so a Hohenstaufen Holy Roman Emperor in the north would completely box in the papal states. Because of this, the Pope, Innocent III (r. 1198-1216), was very much in favor of the Welf candidate, Otto. Innocent offered support to Otto in exchange for promises to obey Church wishes, including not invading southern Italy, and allowing money from vacant German sees to go to Rome. As can be predicted, as soon as Otto ascended the throne, he went back on all of his promises to the papacy. He invaded Italy, and was declared deposed by Innocent, who shifted his support to Frederick II, Frederick I’s grandson.
Frederick II (1194-1250) was crowned Holy Roman Emperor in 1212 on several conditions. He had to abandon all claims to Sicily, follow the direction of the papacy, and lead a crusade. With what is becoming a familiar theme, Frederick broke his promise to the Pope, and united the Holy Roman Empire and Sicily, as well as finding excuse after excuse not to go on crusade. Frederick was excommunicated by Pope Gregory IX in 1227. Frederick ignored this, and was excommunicated again in 1239, with the addition of an interdict wherever he set foot. Frederick then expelled all friars from Sicily and threatened to hang anyone who brought a papal document to him. In response, Gregory IX called a general council to meet in Rome in 1241 to discuss what should be done with Frederick. Frederick issued an order that said to arrest any bishops heading to this council. That same year, Gregory died and was succeeded by pope Innocent IV (r. 1243-1254).
Innocent IV attempted negotiations with Frederick, but failed. He then called a council at Lyons in 1245, where Frederick was declared deposed. An outraged Frederick called upon fellow monarchs of Europe to come with him and rid themselves of the meddlesome papacy. He said that the state had the authority to reform the Church, and that he intended to march on Lyons and imprison the Pope. This did not take place, however, because Louis IX declared that he would bar the way against Frederick if he attempted something so audacious. In 1250, Frederick died, and after the brief reign of his son, the title of Holy Roman Emperor was not held by anyone for nearly 20 years.
The struggle between the Holy Roman Emperors and the Popes had to do with power. Frederick I wanted to end political decentralization and regain power over his arrant lords, Otto IV and Frederick II wanted to increase their control over southern Italy and Sicily. This made the Popes nervous, so they intervened, which only led to more tensions between the Church and the state.