In 1156, Frederick I married Beatrice of Burgundy, daughter and heiress of Renaud III, adding the County of Burgundy, to his estates.

Frederick I who was also known as Frederick Barbarossa was born in 1122 and crowned king of Germany in 1152. In 1158 he was crowned Holy Roman Emperor.

After becoming duke of Swabia in 1147, Frederick accompanied his uncle and king of Germany, Conrad III on the second crusade. His first outing proved disastrous; but all was not lost, Frederick was able to distinguish himself and gain the confidence of his uncle. On his uncle’s death in 1152, Frederick was chosen as the next king of Germany and was crowned at Aix-la-Chapelle becoming Frederick I.

Frederick I was keen to restore the Empire to the position it had occupied under Charlemagne and Otto I the Great and set about issuing a general order for peace. On his accession to the German throne, Frederick I sent news of his election to Pope Eugenius III, but ignored the need to ask for the Popes blessing. Eager to set things right, Frederick obtained a treaty with Rome in 1153, in which he promised to support the Pope in his relations with the rebellious subjects of Rome in return for the Popes acknowledgement of his accession to the throne.

He lead six campaigns into Italy. His first was to be crowned emperor by Pope Adrian IV as a result of the ousting of the Imperial forces of the republican city commune. Frederick I left Italy in the autumn of 1155. Disorder was again rife in Germany, especially in Bavaria, but peace was restored by Frederick's forceful measures and Bavaria was given to his cousin Henry the Lion, duke of Saxony.

In 1156, Frederick I married Beatrice of Burgundy, daughter and heiress of Renaud III, adding the County of Burgundy, to his estates.

1158, Frederick I, accompanied by Henry the Lion set out on his second visit to Italy, resulting in the capture of Milan, and the start of a long conflict with Pope Alexander III. This prolonged disagreement with the Pope, lead to Frederick being excommunicated in 1160. His response was swift; Frederick I declared his support for Antipope Victor IV.

Frederick returned to Germany towards the close of 1162 in time to intervene between Henry the Lion and a number of his neighbouring princes who were growing weary of Henry's power and influence. The next campaign to Italy in 1163 saw his plans for the conquest of Sicily ruined by the formation of a powerful league against him, brought together mainly by the taxes collected by the imperial officers.

In 1166, Frederick I once more journeyed to Italy to secure the claim of his Antipope Paschal, and the coronation of his wife Beatrice as Holy Roman Empress. The trip was halted due to the outbreak of plague forcing the emperor to return to Germany, where he remained for the next six years. Henry the Lion refused to join Frederick on this trip, instead electing to stay behind tending to his own disputes with his neighbours and his continual expansion into Slavic states in northeastern Germany.

Friendly dialog was entered into with the East Roman emperor Manuel, and attempts were made to come to a better understanding with Henry II of England and Louis VII of France.

In 1174, Frederick made his fifth trip to Italy and, in response; the pro-papal Lombard League was formed to stand against him. With the refusal of Henry the Lion to render his support, his campaign was doomed to fail. The consequence of this lack of support was that Frederick suffered a heavy defeat at the battle of Legnano near Milan, where he was wounded and for some time believed to be dead. He sued for peace.

In the Peace of Venice of 1177, Frederick acknowledged the sovereignty of the Papal States, and in return, the Pope acknowledged the Emperor's sovereignty over the Imperial Church. The Lombard cities, however continued to fight until 1183, when, in the Peace of Constance, Frederick ceded the right to freely elect town magistrates.

After settling his differences the Pope, Frederick embarked on the Third Crusade in 1189, with the French army, together with the English, under the leadership of Richard, the Lionheart. Frederick never set foot in the Holy Land as he drowned whilst attempting to cross the River Saleph in Cilicia, southeastern Anatolia.

Frederick’s body was embalmed, and taken back to Germany in a barrel on the back of a cart. His untimely death left the Crusader army under the command of his rivals who had traveled to Palestine separately by sea, and ultimately led to its dissolution.