Editing Frederick Barbarossa (section)

===Second Crusade===
In early 1147, Frederick decided to join the [[Second Crusade]] after his uncle, King Conrad III, had taken the crusader vow in public on 28 December 1146. Frederick's father, [[Frederick II, Duke of Swabia|Duke Frederick II]], strongly objected to this and according to [[Otto of Freising]], the duke berated his brother for permitting his son to go. The elder Frederick, who was dying, expected his son to look after his widow and younger half-brother once he had passed on, not risk his life by going on a crusade.{{sfn|Freed|2016|pp=43–45}} Perhaps in preparation for the crusade, Frederick married [[Adelaide of Vohburg]] sometime before March 1147. His father died on 4 or 6 April and Frederick succeeded him as the Duke of Swabia. The German crusader army departed from [[Regensburg]] seven weeks later.{{sfn|Freed|2016|pp=43–45}}

In August 1147, while crossing the [[Byzantine Empire]], an ill crusader stopped in a monastery outside [[Adrianople]] to recuperate. There he was robbed and killed. Conrad ordered Frederick to avenge him. The duke of Swabia razed the monastery, captured and executed the robbers and demanded they return the stolen money. The intervention of the Byzantine general Prosuch prevented further escalation.{{sfn|Freed|2016|pp=51–53}} A few weeks later, on 8 September, Frederick and [[Welf VI]] were among the few German crusaders who survived when a flash flood destroyed the main camp. They had decided to encamp on a hill a ways away from the main army. The remains of the army reached [[Constantinople]] the following day.{{sfn|Freed|2016|pp=51–53}}

Conrad III attempted to lead the army across Anatolia but finding this too difficult in the face of [[Battle of Dorylaeum (1147)|constant Turkish attacks]] near Dorylaeum, decided to turn back. The rearguard was subsequently annihilated. Conrad sent Frederick ahead to inform King [[Louis VII of France]] of the disaster and ask for help. The two armies, French and German, then advanced together. When Conrad fell ill around Christmas in [[Ephesus]], he returned to Constantinople by ship with his personal retinue, which included Frederick.{{sfn|Freed|2016|pp=51–53}} With Byzantine ships and money, the German army once again left Constantinople on 7 March 1148 and arrived in [[Akko|Acre]] on 11 April. After Easter, Conrad and Frederick visited [[Jerusalem]], where Frederick was impressed by the charitable works of the [[Knights Hospitaller]]. He took part in the [[council of Acre]] on 24 June, where a decision was reached that the crusaders would attack [[Damascus]].{{sfn|Freed|2016|pp=51–53}}

[[File:Crusaders besieging Damascus - Chronique d'Ernoul et de Bernard le Trésorier (late 15th C), f.280v - BL Royal MS 15 E I.jpg|thumb|Crusaders besieging Damascus in 1148]]
The [[Siege of Damascus (1148)|Siege of Damascus]] (24–28 July) lasted a mere five days and ended in failure. [[Gilbert of Mons]], writing fifty years later, recorded that Frederick "prevailed in arms before all others in front of Damascus". On 8 September, the German army sailed out of Acre.{{sfn|Freed|2016|pp=51–53}} On the route home, Conrad III and Frederick stopped in [[Thessaloniki]] where they swore oaths to uphold the treaty that Conrad had agreed with Emperor [[Manuel I Komnenos]] the previous winter. This treaty obligated the Germans to attack King [[Roger II of Sicily]] in cooperation with the Byzantines. After confirming the treaty, Frederick was sent ahead to Germany. He passed through [[Bulgaria]] and [[Kingdom of Hungary (1000–1301)|Hungary]] and arrived in Germany in April 1149.{{sfn|Freed|2016|pp=51–53}}