Otto I was born in 912 to King Henry I of Germany and Mathilda. He married Edith, King Athelstan of England's sister, in 929. After the succession of his father in 936, Otto eagerly developed the policies of the former king. He wanted a strong central power, a feeling smaller German leaders opposed. He also wanted a larger territory, and this wish was very strongly opposed by the people ruling the areas he wanted to claim. To make a long story short, Otto had a lot of fighting to do.
Otto's brother Henry and Duke Eberhard of the Franks rebelled against the king, but suffered defeat at Andernach in 939. Henry submitted to his brother two years later.
To punish King Louis IV of France for assisting the troublemakers, Otto fought against him in 940, with the support of Hugh Capet. In 942 the two kings reached an agreement, however, and later the two of them turned against Hugh. He was defeated in 950.
Fighting for a wife!
Upon receiving a plea for help from the widowed Italian queen, Adelheid, about to be wedded to Berengar II, Otto invaded Italy in 951 and married her himself. Carrying the new title King of the Lombards and the queen home as trophies, he returned to Germany where further rebellion was brewing.
The dukes were feeling their power slipping away as Otto's might grew, and were also said to be jealous of Henry, who had proclaimed duke of Bavaria by Otto. Conrad the Red and Otto's son, Duke Ludolf of Swabia, led the revolt. They were distracted by invading Magyars, however, and when they were ready to turn to Otto again, he had begun to counter their plans.
Fighting with words!
Otto's secret weapon was the Ottonian system. It entailed a closer alliance between the crown and the church and meant more powering to them both. The archbishop of Cologne, Otto's brother Bruno, later duke of Lotharingia, greatly aided him in this.
Fighting old friends!
Back in Italy, Berengar had gathered forces and was making trouble. Pope John XII sent word of this to Otto, and so the king entered Rome in 962 and returned from it an emperor. The title of Holy Roman Emperor, once lost by the Carolingians, had now been restored by the Saxons.
But the words of popes are easily broken, and after a while John XII, who wanted more independence, made friends with Berengar again and welcomed his son to Rome. Slightly vexed by this, Otto marched his army back to the Holy City and summoned a delegation of bishops, while John fled. The absent pope was deposed and a new one, Leo VIII, set in his place.
Otto went away and John returned to take back the holy sceptre. He died soon after, but Benedict V took his place. Otto had to reveal his power yet again and reinstate Leo.
He reached another triumph when the Byzantine Emperor, Nicephorus II Phocus, recognised his worth and gave his daughter in marriage to Otto's son. A year later, in 973, Otto the Great reached his end. He was buried in the cathedral of Magdeburg.