Iconoclasm (Greek for “image-smashing”) was a religious movement against icons (religious portraits) in eighth–ninth century Byzantium. Christian art proliferated in the fourth century because of the patronage of newly Christian emperors and aristocrats.

While the majority of Christians accepted this tendency, a minority, influenced by the biblical injunction against “graven images,” was in opposition. Bishop Eusebius of Caesarea, for example, author of the first work of church history (Ecclesiastical History), was in the latter group and rejected the depiction of Christ in art.

This movement, called iconoclasm, expanded in the seventh century when it emerged in Armenia and reached its largest phase in the Byzantine (Eastern Roman) Empire in the eighth and ninth centuries. (The West experienced its own iconoclastic crisis during 16th century Protestant Reformation.)

Icons vastly increased in popularity in Eastern Christendom in the sixth and seventh centuries, a period when the empire was wracked by Slavs and Bulgars who removed much of the Balkans from imperial control, and by Muslims who seized Syria, Palestine, Egypt, and North Africa. Imperial prestige was greatly reduced and imperial power was weakened by coups, civil strife, and theological controversy.

In this period, people turned for help not to the hapless emperor, but to the icon (a portrait of a saint, angel, or Jesus) found in churches, monasteries, as well as private homes. Icons were often credited with miraculous powers, such as healing from illness or keeping a city safe from enemies.

In the eighth century two bishops in Asia Minor condemned this proliferation of icon prestige among Christians. Emperor Leo III (717–741), who had stopped the Muslims in their siege of Constantinople in 717–718, championed their cause.

Believing that God had given him success and a warning (when a volcanic explosion devastated the island of Thera), he removed the icon that hung before the imperial palace, appointed an iconoclastic patriarch in 730, and issued an edict calling for the destruction of images.

His son and successor Constantine V (741–775), also successful on the battlefield, pressed the iconoclastic cause by persecuting opponents, particularly monks. He also sought to establish a firmer theological basis for iconoclasm by summoning a church council in 754.

Monks like John Damascene, abbot of St. Sabbas Monastery in Palestine, who wrote several treatises defending icons, led opposition to the iconoclasts. The emperor could not arrest John since he lived under Muslim control. John explained that before Jesus, God could not be represented in an icon, but once God became flesh in Jesus, he could be depicted.

Moreover when the icon is used in devotion, the matter is not venerated, but the God of matter who made it. John also distinguished between worship (latreia), which is reserved for God alone, and veneration (proskynesis), which Christians can give to saints and angels. He explained clearly that icon veneration was not idolatry, but true Orthodox practice.

Every pope also opposed iconoclasm. This caused a break of relations between Constantinople and Rome. Emperor Leo III failed in his attempt to arrest the pope but succeeded in removing southern Italy and the Balkans from papal jurisdiction, transferring them to the patriarch of Constantinople.

During this tense period, Rome could not turn to Constantinople for military support against the German Lombards who threatened it. The pope now turned to the Franks, forging an important German-papal alliance that would influence much of the Middle Ages.

In 800 the pope established the precedent of proclaiming the emperor by crowning Frankish king Charlemagne as Roman emperor. Byzantium opposed this act since it viewed the Roman emperor as reigning in Constantinople and crowned by the patriarch.

The first phase of iconoclasm came to an end when Irene, widow of Leo IV (775–780), ruled for her young son Constantine VI. Irene was an iconophile (supporter of icons) and summoned the Seventh Ecumenical Council in Nicaea (787), which declared icons Orthodox. Iconophile emperors ruled from 780 to 813, a period marred by military defeat that led many to believe that God was revealing that iconoclasm had been the “true” doctrine.

An iconoclast general (Leo V) seized the throne and in 815 began the second phase of iconoclasm, deposing the patriarch and summoning a council to restore iconoclasm. Once again the iconoclasts were militarily triumphant. In 820 a coup brought Michael II to power, establishing the Amorian dynasty (820–867). His son, Theophilos (829–842), was the most educated and passionate of the ninth-century iconoclasts.

The great challenge to ninth-century iconoclasm was not foreign adversaries, but internal monastic opposition. Monks were now well organized and they were popularly viewed as heroes. The leading figure was Theodore the Stoudite, abbot of the Stoudios Monastery in Constantinople, whose 1,000 monks were loyal and obedient.

Theodore’s network of support spanned the empire and he worked ceaselessly against iconoclasm. Emperors exiled, beat, and imprisoned him but could not silence him. He died in 826, just prior to the restoration of icons for which he had fought.

The final restoration came in 843 when Empress Theodora ruled as regent for her young son Michael III, successor of Theophilos. By this time the link between iconoclasm and victory had been shattered by a military defeat late in Theophilos’s reign.

Theodora appointed Methodios as the new patriarch, and together they restored adherence to the Seventh Ecumenical Council. This is commemorated each year in the Orthodox Greek Church as “Orthodox Sunday,” on the first Sunday of Lent.

The iconoclast controversy stimulated a revival of learning as iconoclasts searched for manuscripts of the Fathers of the Church to defend their position, while iconophiles, like John Damascene and Theodore the Stoudite, wrote their own treatises. It also led to monasticism’s increased prestige, as monks became the premier champions of Orthodoxy.

The period did—in the end—increase imperial power inasmuch as iconoclast emperors had stabilized the empire against foreign threats and strengthened imperial power domestically. Finally after iconoclasm, the resources for and against iconoclasm, imperial and monastic, respectively, were united together in a great age of missionary activity in central Europe, the Balkans, Russia, and beyond.