According to the text:

   The Last Kingdom is a contemporary story of redemption, vengeance and self-discovery set against the birth of England. The series combines real historical figures and events with fiction, retelling the history of King Alfred the Great and his desire to unite the many separate kingdoms into what would become England.

   Set in the 9th century AD, many of the separate kingdoms of what we now know as England have fallen to the invading Vikings, only the great Kingdom of Wessex stands defiant under its visionary King Alfred the Great. It is the last kingdom. Against this turbulent backdrop lives Uhtred. Born the son of a Saxon nobleman, he is orphaned by the Vikings and then kidnapped and raised as one of their own. Forced to choose between the country of his birth and the people of his upbringing, his loyalties are ever tested. What is he — Saxon or Viking? On a quest to claim his birthright, Uhtred must tread a dangerous path between both sides if he is to play his part in the birth of a new nation and, ultimately, recapture his ancestral lands.

    The Last Kingdom is a show of heroic deeds and epic battles but with a thematic depth that embraces politics, religion, warfare, courage, love, loyalty and our universal search for identity. Combining real historical figures and events with fictional characters, it is the story of how a people combined their strength under one of the most iconic kings of history in order to reclaim their land for themselves and build a place they call home.

Adapted from https://www.bbcamerica.com/shows/the-last-kingdom/about