On the surface, “Vikings” is a mélange of all the juicy ingredients historical drama is known for: There are the requisite blood-soaked battles, the costumes, the customs, and the political and social intrigue. (Although, remarkably and refreshingly, the show is missing a lot of the gratuitous ratings-grabbing sex romps that shows like “Rome and “The Tudors” have doled out like free candy at Halloween.)

But it takes more than bearskin cloaks and battleaxes to keep things interesting over multiple seasons: An audience has to invest in the deeper themes of clan, country, loyalty, and ambition if longevity is to be sustained. And given that we’re now standing on the precipice of the back half of Season 4, with a new fifth season also assured, “Vikings” seems to be succeeding here.

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Besides having plenty of historical events left to plunder for plotlines, “Vikings” still has ample emotional territory to explore as well — in no small part due to the dramatic minefield that unfurled in the first half of Season 4: That long-hallowed storytelling tradition, pitting brother against brother. We watched the rift between Ragnar and Rollo grow deeper as Rollo shifted his allegiance from his brother and their Viking tribe to the French, and to his marriage to Princess Gisla in particular. (And what an ohh la la that proved to be.)

Brother versus brother — more broadly, blood relative versus blood relative — has always offered up a rich vein to mine. While sibling rivalry and/or deep-rooted family tensions are complex psychological phenomena, it’s a little too easy to chalk these plot devices up to little more than some subconscious knee-jerk behavioral pattern from childhood our characters can’t see their way out of.

It’s rarely as cut and dried as mere sibling rivalry or daddy issues: In a properly compelling story, a character usually faces a more complicated dilemma: One in which a cause or new calling rises above the importance of clan. Enter the love interest, the career opportunity — or more simply, a sense of belonging elsewhere — and quite often, all bets are off.

Family allegiance has always been an overly romanticized concept, given that it is essentially an accident of birth. We’re often raised on home-spun homilies about the importance of family — but the truth is that we have no control or choice over which family we are born into. And loyalty is tricky stuff. While considered an important trait by most of us, it must not only be nurtured, but evaluated on an ongoing basis to determine whether it’s doing us more harm, or good. And the evaluation is rarely a simple one.

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If we sever ourselves from our roots altogether, are we doomed to drift aimlessly and suffer an incurable sense of bone-deep rejection for having failed (or been failed by) our first tribe? Our families are our origin story. They provide the foundation upon which we build our first sense of self and identity. Our physical and emotional traits, our socialization, and more, stem from our first tribe.

Of course, the other side of that coin is: how many of us ever truly experience unconditional acceptance by our families? And how much loyalty do we owe to any individual or group that refuses to see us and accept us for who we really are? Thus the conflict of tradition versus self-determination can test long-lived bonds — as it should. We can accept being told who we are by others, or we can find out for ourselves:

BEFORE

rollo before The heart of Vikings is the conflict between cause & clan
Laissez-faire curls all willy-nilly say: “I’m just here to have fun, and kill everyone I see.”

AFTER

rollo after The heart of Vikings is the conflict between cause & clan
A French Court blowout that would make your back crack.

While Rollo has long lived in Ragnar’s legendary shadow, his experiences in Paris provide him with a chance to become his own man. Left behind in foreign territory as the Viking representative, he’s wooed by Emperor Charles with land, titles, and Princess Gisla for a high-born wife. Rollo is initially seduced by all these trappings, without a doubt, because Charles is motivated by the preservation of Paris.

But surprisingly, Rollo seems to actually fall in love with his new French wife in the process. And should we condemn Rollo for educating himself, learning the language and opening himself to the many merits of French culture — especially compared with the more spartan pleasures of Viking life back home? The question becomes: What’s waiting for Rollo back on his home turf, besides an ongoing opportunity to play second fiddle to Ragnar? Characters who decide to forge new destinies for themselves rather than remain confined by the circumstances they are born into are the stuff of legends, after all.

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In the Marvel universe (and the global mythologies before that), Thor and Loki don’t exactly see eye to eye. Ditto for Stefan and Damon of “Vampire Diaries.” Beyond the dueling sibling trope, lack of bloodline loyalty chips away at all branches of fictional family trees. “Game of Thrones’” Tywin Lannister rejected his son, Tyrion, time and again, eventually condemning Tyrion to death — and earning the reverse, eventually, for his troubles. Few fans seemed to blame Tyrion for killing his father in the end, or for throwing his lot in with the Mother of Dragons after she recognizes his skills as a political advisor. While Rowena and Crowley find themselves at more comedic odds in “Supernatural,” we still understand the angst behind the eye rolling. Being free to choose a new tribe or cause or calling is a hard-won battle that pretty much anyone with a less than idyllic upbringing finds some comfort in.

When pressed to choose, characters may reject family loyalty due to love, ambition, or simply because they’ve found a new tribe that feels more like home. In all cases, when they find a new choice that better fits them — something or someone that makes them feel “more than” and not “less than,” something not tethered to the original role they were forced to play in their families — the choice becomes obvious, if not easy. It’s that point of an individual’s evolution at which they get to actively decide who they are.

The story of the Vikings is a tale of conquest, but it’s also one of assimilation. Ragnar, in the end, is a beautiful paragon of the old world, and Rollo the fire-bearer of the new. By casting Rollo as the odd man out, the show keeps him at a distance, wishing for Ragnar’s world to continue just a little longer.

But in the end, Rollo isn’t choosing cause over clan: He’s joining a larger one. And Ragnar — whose greatest love, never forget, is the first Christian he ever met — knows more than a little bit about that.

“Vikings” returns Wednesday, Nov. 30, at 9 p.m. ET/PT, on The History Channel.

Posted by:Julia Diddy