Until recently , what was known about the history of the Viking Age was based on the Icelandic Sagas , the history of the Danes written by Saxo Grammaticus , the Russian Primary Chronicle and the War of the Irish with the Foreigners . Until recently the history of the Viking Age was largely based on Icelandic Sagas , the history of the Danes written by Saxo Grammaticus , the Russian Primary Chronicle and The War of the Irish with the Foreigners .