It's no secret that the sons of Ragnar Lothbrok will be torn apart in "Vikings" season 5. After all, the previous season concluded with the accidental death of Sigurd Snake-In-The-Eye after an enraged Ivar the Boneless threw an axe at him.

So will the Lothbrok brothers go after each other's necks in the fifth season? The possibility has already been confirmed in the show's latest trailer which debuted at the San Diego Comic-Con. But is it possible that Ubbe has a different reason for defying his younger brother in the History series?

Ubbe VS Ivar the Boneless

The SDCC trailer for "Vikings" season 5 confirms that Ubbe will work together with Lagertha (via YouTube). "I will support you against Ivar if you support me against King Harald," the Queen of Kattegat says to Aslaug's eldest son. This statement alone suggests that Ubbe is already plotting against his own brother.

It would be easy to think that Ubbe is still unhappy with what Ivar has done in the season 4 finale. However, there is another hint in the teaser that might point to an ulterior motive for the civil war.Does Ubbe want to rule Kattegat?

Early in the trailer, Ivar is heard declaring that he intends to be King of Kattegat. Although it is obvious that his intention is to kill Lagertha first to claim the throne, the declaration could stir his brothers' ambition of being the successor to Ragnar Lothbrok.

An alliance with Lagertha could be Ubbe's strategy to eventually become the next ruler of Kattegat. It is possible that Lagertha will offer him the chance to rule the kingdom together if he pledges fealty to the current Queen. However, it is highly unlikely that she will die by his hand.

Will Ivar kill Lagertha in 'Vikings' Season 5?

The civil war is happening this season and there is nothing that can stop the bloodshed. But is it also time for Lagertha's rule to end? The Seer has already prophesized that she will be killed by a son of Ragnar Lothbrok. The question is, will it happen in the fifth season?

Ivar has already vowed to avenge his mother who was unfairly murdered by Lagertha.

There is little doubt that the youngest Lothbrok has already forgotten his promise following the death of his own brother.

The stakes are high and deaths are imminent. Is it finally time for Ragnar Lothbrok's heir to take over? Will Lagertha meet her end this fall? Find out who will rule Kattegat after the civil war when "Vikings" season 5 premieres on History on November 29.