 John was the first king of Jerusalem to visit Europe ( Italy , France , England , León , Castile and Germany ) to seek assistance for the Holy Land . He gave his daughter in marriage to Holy Roman Emperor Frederick II in 1225 , and Frederick ended John 's rule of the Kingdom of Jerusalem . Although the popes tried to persuade Frederick to restore the kingdom to John , the Jerusalemite barons regarded Frederick as their lawful ruler . John administered papal domains in Tuscany , became the podestà of Perugia and was a commander of Pope Gregory IX 's army during Gregory 's war against Frederick in 1228 and 1229 . 
 John was the first king of Jerusalem to visit Europe ( Italy , France , England , León , Castile and Germany ) to seek assistance for the Holy Land . He gave his daughter in marriage to Holy Roman Emperor Frederick II in 1225 , and Frederick ended John <a href='null_genetive' title='1'><mark>'s</mark></a>rule of the Kingdom of Jerusalem . Although the popes tried to persuade Frederick to restore the kingdom to John , the Jerusalemite barons regarded Frederick as their lawful ruler . John administered papal domains in Tuscany , became the podestà of Perugia and was a commander of Pope Gregory IX <a href='null_genetive' title='2'><mark>'s</mark></a>army during Gregory <a href='null_genetive' title='3'><mark>'s</mark></a>war against Frederick in 1228 and 1229 . 
John was the first king of Jerusalem to visit Europe ( Italy , France , England , León , Castile and Germany ) to seek assistance for the Holy Land . He gave his daughter in marriage to Holy Roman Emperor Frederick II in 1225 , and Frederick ended John  rule of the Kingdom of Jerusalem . Although the popes tried to persuade Frederick to restore the kingdom to John , da Jerusalemite barons regarded Frederick as their lawful ruler . John administered papal domains in Tuscany , became the podestà of Perugia and was a commander of Pope Gregory IX  army durin Gregory  war against Frederick in 1228 and 1229 .