<P> The retreat of Roman forces in the 5th century facilitated the landing of migrants from what is now Germany and created the kingdom of the South Saxons under King Ælle, who is recorded as having held overlordship over other Anglo - Saxon kingdoms and the first bretwalda, or' Britain ruler' . Under St Wilfrid, Sussex became the last of the seven traditional kingdoms of the heptarchy to undergo Christianisation . By the 8th century the kingdom had expanded to include the territory of the Haestingas . Around 827 in the aftermath of the battle of Ellandun, Sussex was annexed by the kingdom of Wessex, a kingdom that with further expansion became the kingdom of England . </P> <P> In 1066 Norman forces arrived in Sussex, the heartland of King Harold Godwinson . Defeating Harold at the Battle of Hastings, William the Conqueror established five (later six) semi-independent territories known as rapes . The South Saxon see was transferred from Selsey Abbey to a new cathedral in the city of Chichester . Castles were built, many the subject of sieges in the High Middle Ages . Sussex was of strategic importance on the most direct route between Angevin lands in England and Normandy . Many Sussex ports, including the Cinque Ports, provided ships for military use . A succession crisis in the kingdom of France led to the Hundred Years War in which Sussex found itself on the frontline . Various rebellions followed in the late medieval period including the Peasants' Revolt, Jack Cade's rebellion and the rebellion of the Merfold brothers . </P> <P> Under Henry VIII, the church in England withdrew from Rome . Mary I returned England to Catholicism and in Sussex 41 Protestants were burned to death . Under Elizabeth intolerance continued on a lesser scale as many Catholics in Sussex lost their lives at this time . In Elizabeth's reign, Sussex was open to the older Protestant forms practised in the Weald as well as the newer Protestant forms coming from Continental Europe; combined with a significant Catholic presence, Sussex was in many ways out of step with the rest of southern England . Sussex escaped most of the ravages of the Civil War with two sieges and one battle . As the Industrial Revolution took hold, the Wealden iron industry collapsed . The growth of the seaside resorts in the 18th century was especially significant in Sussex . At the Battle of the Boar's Head Sussex men played a significant role in the World War One, which ended when the terms of Germany's Armistice were agreed at Danny House . In World War Two the county was a base for the Dieppe Raid and D - Day landings . In 1974, the Lord - Lieutenant of Sussex was replaced with one each for East and West Sussex, which became separate ceremonial counties . In the 21st century a county day and a county flag were created for Sussex and a National Park was established for the South Downs . </P> <P> In 1993 a human - like tibia was found at Boxgrove near Chichester . Then in 1996 further hominid remains were found: two incisor teeth from a single individual recovered from the lower freshwater deposits at the site . The remains came to be known as "Boxgrove man" and are thought to be a species known as Homo heidelbergensis . Boxgrove man apparently lived in a temperate stage immediately prior to the Anglian glaciation, in the Lower Paleolithic period between 524,000 and 478,000 years ago . </P>

When was sussex divided into east and west