 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 <unk> tried to persuade Frederick to restore the kingdom to John , the Jerusalemite barons regarded Frederick as their lawful ruler . John administered papal domains in <unk> , became the <unk> of Perugia and was a commander of Pope Gregory IX 's army during Gregory 's war against Frederick in 1228 and 1229 . 
