"The Great Army" is the seventeenth episode of the fourth season of Vikings. It is the forty-sixth episode of the series overall. It first aired on January 11, 2017. It was written by creator Michael Hirst and directed by Jeff Woolnough.
The Viking army begins to gather in Kattegat; Lagertha must remain vigilant in the absence of her son, Bjorn.
Ubbe, Sigurd and Ivar agree to gather a large army to take to England and avenge Ragnar. Rollo returns to Francia, offering land in Normandy to any Vikings willing to settle. Halfdan introduces Harald to Egil, the bastard son of an earl. Judith meets King Aelle and tries to convince him to ally with Ecbert against the coming Viking attack, but Aelle refuses. In Wessex, Ecbert continues to groom Alfred as future king. and warns him not to trust others, but think for himself. An armada of Swedish vikings, lead by Earl Jorgensen, arrive to join the Lothbroks in revenge. Ivar and Ubbe attempt to kill Lagertha, but are stopped by Bjorn, who greets his mother coldly. Bjorn makes clear that his brothers will have to kill him before Lagertha. Torvi advises Bjorn not to join Ivar in vengence, which causes Bjorn to lash out against her. Bjorn leaves her in a fit of rage and has an encounter with Astrid. Floki presents Ivar with a war chariot which will allow him to lead troops in combat.
- Katheryn Winnick as Lagertha
- Clive Standen as Rollo
- Gustaf Skarsgård as Floki
- Alexander Ludwig as Bjorn
- Peter Franzén as King Harald "Finehair"
- Jasper Pääkkönen as Halfdan "The Black"
- Alex Høgh as Ivar
- Marco Ilsø as Hvitserk
- David Lindström as Sigurd
- Jordan Patrick Smith as Ubbe
- Linus Roache as King Ecbert
- Josefin Asplund as Astrid
- Maude Hirst as Helga
- Ivan Kaye as King Aelle
- Ida Marie Nielsen as Margrethe
- Georgia Hirst as Torvi
- Jennie Jacques as Princess Judith
- Morgane Polanski as Princess Gisla
Additional Cast (in order of appearance)
- Sinead Gormally as Tanaruz
- Charlie Kelly as Egil
- Tristan Heanue as Blacksmith
- Cathy White as Ealhswith
- Caitlin Scott as Blaeja
- Charles Last as William Son of Rollo
- Isaac O'Sullivan as Alfred
- Adam Traynor as First Viking
- Donal Gallery as Second Viking
- Jack Nolan as Earl Jorgensen
- Anton Giltrap as Guthrum