Frederick I Barbarossa was born in 1122, to Frederick II, Duke of Swabia and his wife Judith. Members of the Hohenstaufen dynasty and House of Welf respectively, Barbarossa's parents provided him with strong family and dynastic ties which would aid him later in life. At the age of 25, he became the Duke of Swabia following his father's death. Later that year, he accompanied his uncle, Conrad III, King of Germany, on the Second Crusade. Thought the crusade was a tremendous failure, Barbarossa acquitted himself well and earned the respect and trust of his uncle.
King of Germany:
Returning to Germany in 1149, Barbarossa remained close to Conrad and in 1152, was summoned by the king as he lay on his death bed. As Conrad neared death, he presented Barbarossa with the Imperial seal and expressed his desire that the thirty-year old duke succeed him as king. This conversation was witnessed by the Prince-Bishop of Bamberg who later stated that Conrad was in full possession of his mental powers when he named Barbarossa his successor. Moving quickly, Barbarossa garnered the support of the prince-electors and was named king on March 4, 1152.
As Conrad's six-year old son had been prevented from taking his father's place, Barbarossa named him Duke of Swabia. Ascending to the throne, Barbarossa wished to restore Germany and the Holy Roman Empire to the glory it had achieved under Charlemagne. Traveling through Germany, Barbarossa met with the local princes and worked to end sectional strife. Using an even hand, he united the princes' interests while gently reasserting the power of the king. Though Barbarossa was King of Germany, he had not yet been crowned Holy Roman Emperor by the pope.
Marching to Italy:
In 1153, there was general feeling of dissatisfaction with the papal administration of the Church in Germany. Moving south with his army, Barbarossa sought to calm these tensions and concluded the Treaty of Constance with Pope Adrian IV in March 1153. By the terms of the treaty, Barbarossa agreed to aid the pope in fighting his Norman enemies in Italy in exchange for being crowned Holy Roman Emperor. After suppressing a commune led by Arnold of Brescia, Barbarossa was crowned by the Pope on June 18, 1155. Returning home that fall, Barbarossa encountered renewed bickering among the German princes.
To calm affairs in Germany, Barbarossa gave the Duchy of Bavaria to his younger cousin Henry the Lion, Duke of Saxony. On June 9, 1156, at Würzburg, Barbarossa married Beatrice of Burgundy. Never idle, he intervened in a Danish civil war between Sweyn III and Valdemar I the following year. In June 1158, Barbarossa prepared a large expedition to Italy. In the years since he was crowned, a growing rift had opened between the emperor and the pope. While Barbarossa believed that the pope should be subject to the emperor, Adrian, at the Diet of Besançon, claimed the opposite.
Marching into Italy, Barbarossa sought to reassert his imperial sovereignty. Sweeping through the northern part of the country, he conquered city after city and occupied Milan on September 7, 1158. As tensions grew, Adrian considered excommunicating the emperor, however he died before taking any action. In September 1159, Pope Alexander III was elected and immediately moved to claim papal supremacy over the empire. In response to Alexander's actions and his excommunication, Barbarossa began supporting a series of antipopes beginning with Victor IV.
Traveling back to Germany in late 1162, to quell unrest caused by Henry the Lion, he returned to Italy the following year with the goal of conquering Sicily. These plans quickly changed when he was required to suppress uprisings in northern Italy. In 1166, Barbarossa attacked towards Rome at won a decisive victory at the Battle of Monte Porzio. His success proved short-lived as disease ravaged his army and he was forced to retreat back to Germany. Remaining in his realm for six years, he worked to improve diplomatic relations with England, France, and the Byzantine Empire.
During this time, several of the German clergy had taken up the cause of Pope Alexander. Despite this unrest at home, Barbarossa again formed a large army and crossed the mountains into Italy. Here he met the united forces of the Lombard League, an alliance of northern Italian cities fighting in support of the pope. After winning several victories, Barbarossa requested that Henry the Lion join him with reinforcements. Hoping to increase his power through the possible defeat of his uncle, Henry refused to come south.
On May 29, 1176, Barbarossa and detachment of his army were badly defeated at Legnano, with the emperor believed killed in the fighting. With his hold over Lombardy broken, Barbarossa made peace with Alexander at Venice on July 24, 1177. Recognizing Alexander as pope, his excommunication was lifted and he was reinstated into the Church. With peace declared, the emperor and his army marched north. Arriving in Germany, Barbarossa found Henry the Lion in open rebellion of his authority. Invading Saxony and Bavaria, Barbarossa captured Henry's lands and forced him into exile.
Though Barbarossa had reconciled with the pope, he continued to take actions to strengthen his position in Italy. In 1183, he signed a treaty with the Lombard League, separating them from the pope. Also, his son, Henry, married Constance, the Norman princess of Sicily, and was proclaimed King of Italy in 1186. While these maneuvers led to increased tension with Rome, it did not prevent Barbarossa answering the call for the Third Crusade in 1189.
Working in conjunction with Richard I of England and Philip II of France, Barbarossa formed an immense army with the goal of retaking Jerusalem from Saladin. While the English and French kings traveled by sea to the Holy Land with their forces, Barbarossa's army was too large and was forced to march overland. Moving through Hungary, Serbia, and the Byzantine Empire, they crossed the Bosporus into Anatolia. After fighting two battles, they arrived at the Saleph River in southeast Anatolia. While stories vary, it is known that Barbarossa died on June 10, 1190, while jumping into or crossing the river. His death led to chaos within the army and only a small fraction of the original force, led by his son Frederick VI of Swabia, reached Acre.