First things first, we had to ask the Hunger Games star about his character's noticeable transformation since the series' time jump.
"It's been a really long, grueling process of making this character," explained Ludwig, who was 21 when he joined season two of the series as teenage Bjorn. "Playing a boy when you're a man yourself is really tough, so it's nice to finally be able to play something that is in my range. I waited so long to be able to do this, so I'm happy that it's resonating."
Bjorn's longer beard isn't the only sign of change in the character -- he's also seemed to grow confidence, power and leadership in Ragnar's (Travis Fimmel) absence.
"There will always be a lot of respect, however, [Bjorn] really is questioning why his father would come back after so many years," Ludwig said of Ragnar. "He's such a broken man. You're like, 'Where's that spark? Where's that energy that he had?'"
In comparison, "Bjorn has taken on such big responsibility... He's not this boy anymore. He's this leader with strength and complexity that drives from these tortured relationships he's had to have with his father and his uncle… He's kind of taken control over the place," the 24-year-old actor offered, before noting that Bjorn stays loyal to his father by not assuming kingship. "To him, that's not his ambition. What he really wants to do is explore."
Wednesday's episode, appropriately titled "Two Journeys," focused on Bjorn's attempt at Mediterranean exploration, which was unfortunately halted by Rollo (Clive Standen), who insisted on coming along for the ride.
"If he could, [Bjorn] would kill [Rollo] without question. As far as he is concerned, he's not his uncle anymore," Ludwig said, reflecting on Rollo's seeming betrayal of his Viking people during the show's mid-season finale in April. "The only reason he doesn't is because he's a smart leader. Rollo controls the only part of the known world that can lead them into new lands."
Bjorn may be forced to keep Rollo alive, but that didn't stop him from almost drowning his uncle.
"Basically what that was was a power play," Ludwig confessed, nonchalantly. "He's saying, 'I could kill you at any moment if I wanted to. I'm not going to, because I'm smarter than that, but just so you know, I'm the leader here.'"
While Bjorn leads his Mediterranean expedition in Wednesday's episode, it's his mother, Lagertha (Katheryn Winnick), who audiences saw start to plot her revenge on Aslaug (Alyssa Sutherland) to takeover Kattegat -- which Ludwig says Bjorn is "not aware of" at this point, but is "something he's wanted to do for a long time."
"He's had to be really politically smart and he's had to put a lot of his emotions aside," he explained. "I think it's going to build up and explode in him really soon, because you can only hide so much for so long."
Though Bjorn might struggle in managing his responsibilities, Ludwig insists this is the Bjorn -- and season of Vikings -- we've all been waiting for.
"The end of this is without question the most epic battle we've ever filmed. We had more extras than they had on Braveheart," he revealed. "You're running opposite hundreds and hundreds of horses coming at you…It's just this ridiculous battle, and I think the audience is going to really, really look forward to that."
"He's finally his own man, and becoming the legend that is Bjorn Ironside, so now it's about him carving his own path," Ludwig said. "This was the season that I was promised when I signed onto the show, and it was a lot of years of me being incredibly patient and just hoping that we get to this season, and hoping that I get to showcase what was promised to me."
"It's a hard transition, because obviously Travis [Fimmel] is just an incredible actor, and he's built such an amazing character. Not only that, but he's been an amazing mentor to me, and an incredible friend," the Canadian actor shared. "But I think you'll slowly find yourself getting immersed in [Bjorn's] journey. It gets super exciting. You've never seen Vikings in this kind of environment."
As for the three words Ludwig would use to describe Bjorn's journey through the rest of the season? "I would say riveting, challenging and dark," he promised. "I think it will be really, really cool for everyone to see what's about to reveal itself."
Vikings airs Wednesdays at 9 p.m. ET/PT on History Channel.