Vikings season 4 is supersized, and the 20-episode run will take the story of Ragnar's rule across more than a decade.

'Vikings' Season 4: Clive Standen Lands Lead In 'Taken', Is This The End Of Rollo?

From season 1 through season 3, we saw Bjorn (Alexander Ludwig) grow from a boy to a man. Over the course of season 4, we will see him morph into the leader he was always meant to be. Considering the prince's current predicament however, his rise to power won't happen anytime soon.

"The season's so long," Ludwig told TV Insider. "It's got to be like 15 years."

'Vikings' Season 4: Did You Catch That Major Teaser For Bjorn's Future? Easter Egg Explained

Over that time, Bjorn will start to see his father start to fade and falter. Ragnar (Travis Fimmel) never wanted to be king, and the older Fimmel's character gets, he will become a shadow of the warrior we once knew.

"You'll see him become ready [to be king] this season," Ludwig teased. "As the season continues, Bjorn sees his father go through internal turmoil. Bjorn's pained by this, but realizes that if his father is incapable of leading the army, then he has to. He's got to step up. You're going to see a big change in power."

Bjorn won't be the only one angling for his father's throne, however. The seer prophesied that a woman will take power, and we all know Aslaug (Alyssa Sutherland) is angling to become the subject of the blind man's prognostications. Harald Fairhair (Peter Franzén) will also become a contender, and it remains to be seen which of these three hopefuls will eventually rule Kattegat.

Catch Vikings Thursdays at 10 p.m. ET on the History Channel. Click the video below to see a preview for the series' next episode, "Kill the Queen."