In 938, a rich vein of silver was discovered at the Rammelsberg in Saxony. This mineral wealth helped fund Otto's activities throughout his reign; indeed, it would provide much of Europe's silver, copper, and lead for the next two hundred years.
Otto's early reign was marked by a series of ducal revolts. In 938, Eberhard, the new duke of Bavaria, refused to pay Otto homage. After Otto deposed him in favor of his uncle Berthold, Eberhard of Franconia revolted, together with several of the Saxon nobility, who tried to replace Otto with his elder half-brother Thankmar (son of Henry's first wife Hatheburg). While Otto was able to defeat and kill Thankmar, the revolt continued the next year when Gilbert, the duke of Lorraine, swore fealty to King Louis IV of France. Meanwhile, Otto's younger brother Henry conspired with Frederick, Archbishop of Mainz, to assassinate him. The rebellion ended in 939 with Otto's victory at the Battle of Andernach, where the dukes of Franconia and Lorraine both perished. Henry fled to France, and Otto responded by supporting Hugh the Great in his campaign against the French crown, but in 941 Otto and Henry were reconciled through the efforts of their mother, and the next year Otto withdrew from France after Louis recognized his suzerainty over Lorraine.
To prevent further revolts, Otto arranged for all the important duchies in the German kingdom to be held by close family members. He kept the now-vacant duchy of Franconia as a personal fiefdom, while in 944 he bestowed the duchy of Lorraine upon Conrad the Red, who later married his daughter Luitgard. Meanwhile, he arranged for his son Liutdolf to marry Ida, the daughter of Duke Herman of Swabia, and to inherit that duchy when Herman died in 947. A similar arrangement led to Henry becoming duke of Bavaria in 949.
Meanwhile, Italy had fallen into political chaos. On the death (950), possibly by poisoning, of Lothair of Arles, the Italian throne was inherited by a woman, Adelaide of Italy, the respective daughter, daughter-in-law, and widow of the last three kings of Italy. A local noble, Berengar of Ivrea, declared himself king of Italy, abducted Adelaide, and tried to legitimize his reign by forcing Adelaide to marry his son Adalbert. However, Adelaide escaped to Canossa and requested German intervention. Luidolf and Henry independently invaded northern Italy to take advantage of the situation, but in 951 Otto frustrated his son's and his brother's ambitions by invading Italy himself. He received the homage of the Italian nobility, assumed the title "King of the Lombards" and in 952 forced Berengar and Adalbert to pay homage, allowing them to rule Italy as his vassals. Having been widowed since 946, he married Adelaide himself.
When Adelaide bore a son, Liudolf feared for his position as Otto's heir. In 953 he rebelled in league with Conrad, Duke of Lorraine and the Archbishop of Mainz. While Otto was initially successful in reasserting his authority in Lorraine, he was captured while attacking Mainz, and by the next year, the rebellion had spread throughout the kingdom. However, Conrad and Liudolf erred by allying themselves with the Magyars. Extensive Magyar raids in southern Germany in 954 compelled the German nobles to reunite, and at the Diet of Auerstadt, Conrad and Luitdolf were stripped of their titles and Otto's authority reestablished. In 955, Otto cemented his authority by routing Magyar forces at the Battle of Lechfeld (10 August 955) and the Obodrites at the Battle of Recknitz (16 October 955).
As a key element of his domestic policy, Otto sought to strengthen ecclesiastical authorities, chiefly bishops and abbots, at the expense of the secular nobility who threatened his own power. To control the forces that the Church represented, Otto made consistent use of three institutions. One was the royal investiture of bishops and abbots with the symbols of their offices, both spiritual, for Otto was the anointed King of the Germans, and temporal, in which Otto secured his bishops and abbots as his vassals through a commendation ceremony. "Under these conditions clerical election became a mere formality in the Ottonian empire, and the king filled up the ranks of the episcopate with his own relatives and with his loyal chancery clerks, who were also appointed to head the great monasteries" (Cantor, 1994 p. 213). The second institution was more securely established in Ottonian territories, that of the proprietary churches (Eigenkirchen; in English law the right of "advowson"). In German law, any structure built on land owned by a lord belonged to that lord, unless a charter had very specifically conveyed away those rights. Otto and his chancery aggressively reclaimed proprietary rights over many landed churches and abbeys. The third instrument of Ottonian power was the system of the advocatus (German Vogt). The advocatus was a secular manager of ecclesiastical estates, who was entitled to a certain shares of the agricultural produce and other revenues and was responsible for safety and good order. Unlike countships, which quickly became hereditary, the Vogt performed the duties of a West Frankish bailli and held his position solely at the continued will of the emperor whom he served.
Otto endowed the bishoprics and abbeys with large tracts of land, over which secular authorities had neither the power of taxation nor legal jurisdiction. In an extreme example, when Conrad the Red was stripped of his ducal title in Lorraine, Otto appointed his brother Bruno, already the Archbishop of Cologne as the new duke of Lorraine. In the lands Otto conquered from the Wends and other Slavic peoples on his eastern borders, he founded several new bishoprics.
Because Otto personally appointed the bishops and abbots, these reforms strengthened his central authority, and the upper ranks of the German church functioned in some respect as an arm of the imperial bureaucracy. Conflict over these powerful bishoprics between Otto's successors and the growing power of the Papacy during the Gregorian Reforms would eventually lead in the 11th century to the Investiture Conflict and the undoing of central authority in Germany.
In the early 960s, Italy was again in political turmoil, and when Berengar occupied the northern Papal States, Pope John XII asked Otto for assistance. Otto returned to Italy and on February 2 962, the pope crowned him emperor. See Translatio imperii. Ten days later, the pope and emperor ratified the Diploma Ottonianum, under which the emperor became the guarantor of the independence of the papal states. This was the first effective guarantee of such protection since the Carolingian Empire. After Otto left Rome and reconquered the Papal States from Berengar, however, John became fearful of the emperor's power and sent envoys to the Magyars and the Byzantine Empire to form a league against Otto. In November 963, Otto returned to Rome and convened a synod of bishops that deposed John and crowned Leo VIII, at that time a layman, as pope. When the emperor left Rome, however, civil war broke out in the city between supporters of the emperor and of John. John returned to power amidst great bloodshed and excommunicated those who had deposed him, forcing Otto to return to Rome a third time in July 964 to depose Pope Benedict V (John having died two months earlier). On this occasion, Otto extracted from the citizens of Rome a promise not to elect a pope without imperial approval.
Otto unsuccessfully campaigned in southern Italy on several occasions from 966 to 972. In 967, he gave the duchy of Spoleto to Pandulf Ironhead, prince of Benevento and Capua, a powerful ally in the Mezzogiorno. In the next year (968) Otto left the siege of Bari in the charge of Pandulf, but the allied duke was captured in the battle of Bovino by the Byzantines. In 972, the Byzantine emperor John I Tzimisces recognized Otto's imperial title and agreed to a marriage between Otto's son and heir Otto II and his niece Theophano. Pandulf was released from captivity.
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