Cissa is part of an Anglo-Saxon invasion force that lands in three ships at a place called Cymensora in 477.
The invasion is led by Cissa's father Ælle and includes his two brothers.
They are said to have fought against the local Britons.
Their conquest of what became Sussex, England continues when they fight a battle on the margins of Mecredesburne in 485 and Pevensey in 491 where they are said to have slaughtered their opponents to the last man.
The main source for this story is the Anglo Saxon Chronicle, a series of annals written in the vernacular Old English.
The Anglo Saxon Chronicle was commissioned in the reign of Alfred the Great some 400 years after the landing at Cymenshore.
One of the purposes of the chronicle was to provide genealogies of the West Saxon kings.
Although a lot of the facts provided by the chronicle can be verified, the foundation story of Sussex involving Ælle and his three sons can not.
It is known that Anglo-Saxons did settle in eastern Sussex during the fifth century, but not in the west where Cymensora was probably situated.
The city of Chichester, whose placename is first mentioned in the Anglo-Saxon Chronicle, of 895 CE, is supposedly named after Cissa.
