Offa (757–796), was the first of the Anglo-Saxon kings who might rightly be called "king of the English". He was the son of Thingfrith, the brother of Penda. He struggled to gain control of Mercia having come to power just after a civil war. But he proved to be ruthless, bold and creative in bringing Kent, Sussex and Essex under his control. Offa had diplomatic relations with Charlemagne. He was one of the few Anglo-Saxon monarchs to have dealings with continental rulers. Letters and presents were exchanged. But when Offa sought a marriage of his son to one of Charlemagne's daughters, relations were quickly cut off. Frankish ports were closed to British ships. Offa, very involved in church affairs, presided over church councils personally in 786-7. In 787 he convinced the pope to create the position of archbishop of Lichfield in Mercia. He wanted his own archbishop who was closer at hand than the Archbishop of Canterbury. He reorganized the of his kingdom. One of these defenses, Offa's Dyke was a massive earthworks between Mercia and the Welsh kingdoms to the west. Offa died in 796. His son, Ecgfrith, lasted only 141 days as king. Mercia was never again as powerful as it was during Offa's reign.