The Holy Roman Empire was a loosely joined union of smaller kingdoms which held power in western and central Europe between A.D. 962 and 1806. It was ruled by a Holy Roman Emperor who oversaw local regions controlled by a variety of kings, dukes, and other officials. The Holy Roman Empire was an attempt to resurrect the Western empire of Rome.
Many people confuse the Holy Roman Empire with the Roman Empire that existed during the New Testament period. However, these two empires were different in both time period and location. The Roman Empire (27 B.C.–A.D. 476) was based in Rome (and, later, Constantinople) and controlled nations around the Mediterranean rim, including Israel. The Holy Roman Empire came into existence long after the Roman Empire had collapsed. It had no official capital, but the emperors—usually Germanic kings—ruled from their homelands.
In the fourth century, Christianity was embraced by the emperor and was pronounced the official religion of the Roman Empire. This blending of religion and government led to an uneasy but powerful mix of doctrine and politics. Eventually, power was consolidated in a centralized Roman Catholic Church, the major social institution throughout the Middle Ages. In A.D. 1054, the Eastern Orthodox Church separated from the Western (Roman) Church, in part due to Rome’s centralized leadership under the Pope.
Pope Leo III laid the foundation for the Holy Roman Empire in A.D. 800 when he crowned Charlemagne as emperor. This act set a precedent for the next 700 years, as the Popes claimed the right to select and install the most powerful rulers on the Continent. The Holy Roman Empire officially began in 962 when Pope John XII crowned King Otto I of Germany and gave him the title of “emperor.” In the Holy Roman Empire, civil authority and church authority clashed at times, but the church usually won. This was the time when the Catholic Popes wielded the most influence, and the papacy’s power reached its zenith.
During the Middle Ages, a wide variety of new church traditions became official doctrine of the Roman Church. Further, the church-state engaged in many military conflicts, including the Crusades.
Late in the period of the Holy Roman Empire, a growing number of Christians grew uneasy with the dominance, teaching, and corruption of the Roman Catholic Church. In the 1500s, Martin Luther launched the Protestant Reformation. John Calvin became a Reformation leader based in Geneva, Switzerland, and others, including Ulrich Zwingli and a large Anabaptist movement, helped reform religion in the Western world.
The major theological issues in the Reformation focused on what are known as the five solas (five “only’s”), which expressed the primacy of biblical teaching over the authority of the Pope and sacred tradition. Sola gratia, the teaching of salvation by “grace alone” through faith alone in Christ alone, empowered a new era of evangelistic outreach in Europe that extended to those who would later colonize North America. Sola scriptura, or “Scripture alone,” taught that the Bible was the sole authority on matters of faith. This teaching led to the development of new churches outside of the Catholic system and the development of new statements of faith for the many Protestant groups founded during this time. The Holy Roman Empire continued to hold power after the Reformation, but the seeds of its demise had been sown; after the Reformation, the Church’s imperial influence waned and the authority of the Pope was curtailed. Europe was emerging from the Middle Ages.
In summary, the Holy Roman Empire served as the government over much of Europe for the majority of medieval history. The Roman Catholic Church, melded in a church-state alliance with the emperor, was the major religious entity. The Church encountered numerous changes even as it amassed land and political clout. Late in this period, Martin Luther and other Reformers transformed the way religion was practiced in central Europe, and their work continues to influence many around the world today.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.