'Vikings' season 4 midseason finale spoilers: Who will survive Ragnar and Rollo's fight?

Rollo (Clive Standen) and Ragnar (Travis Fimmel) in Vikings season 4.History Channel

The highly anticipated battle between Ragnar Lothbrok (Travis Fimmel) and his traitorous brother Rollo (Clive Standen) will finally happen in the midseason finale of "Vikings" season 4.

In the trailer for the episode titled "The Last Ship," Ragnar appears very eager to start their war versus Paris. But this time, his intention for the attack is not meant to raid the flourishing city. Instead, he aims to have a one-on-one combat with Rollo, who betrayed him when he made a pact with Emperor Charles.

According to the synopsis for the episode, "A fierce battle between the Vikings and the French eventually comes down to Ragnar against Rollo and the outcome seals the fates of the two brothers."

Ragnar has been in bad shape since the end of season 3, when he was fatally wounded during their previous raid in Paris. He was also struggling with his dependence on the drug given by Yidu (Dianne Doan). But his determination to kill his brother gives him enough strength to look forward to their biggest battle to date.

On the other hand, Rollo is also prepared to end his brother's life in order to step out of his shadows and prove that he is better than Ragnar. This could mean that their upcoming battle will be bloodier than ever.

Meanwhile, the trailer also revealed that Ragnar's ex-wife Lagertha's (Katheryn Winnick) life could also be in danger in the upcoming episode as a French warrior pierced a sword right through her breast plate.

In the previous episode, Lagertha suffered from the loss of a child. She already knew it was coming, since the Seer (John Kavanagh) already told her about it a long time ago. But she was still hurt when the child died. Will she also suffer the same fate as her dead baby?

The midseason finale of "Vikings" season 4 airs Thursday, April 21, on History Channel.