Sixth Crusade
The Lombard League was renewed several times and upon the death of Frederick I's son Henry VI in 1197 once again gained prestige, while Henry's minor son, Frederick II, elected king, had to fight for the throne against his Welf rival Otto IV. In 1226 Frederick, sole king since 1218 and emperor since 1220, aimed to convene the princes of the Holy Roman Empire in Italy in order to prepare the Sixth Crusade.