The events of “The Promise” transpire some 30 years prior to the storyline of “Casablanca,” but we can’t help but be reminded of the latter film when we witness this love triangle set against the backdrop of the horrors of a world war.

Of course nobody ever says, “I’m no good at being noble, but it doesn’t take much to see that the problems of three little people don’t amount to a hill of beans in this crazy world.” But there’s a moment when Christian Bale’s antihero American journalist seems to be thinking exactly that as he and Oscar Isaac’s medical student compete for the love of Charlotte Le Bon’s Armenian-French teacher.

Two men in love with the same woman, who is torn between her loyalty to one and the intense feelings she has for the other. That would be complicated enough, but considering matters unfold just as Turkey is entering World War I, leading to the Armenian Genocide in which some 1.5 million people were murdered by the Turkish government, and that all three of the main players get caught up in one harrowing and often heartbreaking situation after another, this is one intense and draining (and sometimes plausibility-stretching) story.

Speaking with a precise, nearly delicate Armenian accent, Isaac’s Michael narrates the sweeping story, which begins with him working as an apothecary and aspiring doctor in his small and peaceful village.

Michael agrees to marry a local girl because her father’s dowry is the only way he’ll be able to pay for medical school. He doesn’t love her, but he figures that will come with time.

(We want to tell the guy: Stop brooding, Michael. You’re being set up with Angela Sarafyan, who plays one of the impossibly beautiful robots in “Westworld.” And her character of Maral is sweet, kind, loving and pretty much all-around wonderful. You should be so lucky.)

Velvet pouch of money in hand, Michael sets out for Constantinople and the opulent home of his father’s cousin, a local merchant. There it takes all of about one week for Michael to fall completely in love with Ana (Charlotte Le Bon), who tutors his cousin’s children and thus is always conveniently hanging around the house.

Ah, but Ana is with Christian Bale’s Chris, a brave, macho, famous, globetrotting American journalist with the Associated Press. Even though Chris drinks too much, shoots his mouth off too often and has a fiery temper, he’s got a noble heart, and his love for Ana is fierce. Chris is smart enough to see there’s an intense spark between Ana and Michael, but he’s not about to give her up without a fight.

Meanwhile, Michael is torn about his feelings for Ana, because he DID make a promise to Maral back home, and he takes that pledge seriously.

The romantic complications often take a back seat once the focus shifts to the outbreak of war. Chris rides into the thick of things as a war correspondent; Ana desperately tries to protect more than a dozen orphaned children, and Michael’s attempt to save his father’s cousin results in Michael landing in a prison work camp, where he will toil until he drops dead.

Director and co-writer Terry George (who delivered a much more powerful film about genocide with “Hotel Rwanda” in 2004) is a master at delivering unforgettable set pieces, as when Michael finds himself clinging to the side of a speeding train in the dead of night and comes to realize the train cars are filled with Armenian prisoners being sent to their death.

Oscar Isaac’s Michael is the primary focus, but for long stretches the film concentrates on Bale’s Chris, who becomes a much more sympathetic and complex character when he’s on his own and he’s not railing against Ana for her betrayal or shooting withering glances at Michael. Even when Chris’ heart is shattered, he’s the kind of man who puts his personal feelings aside and risks all for the greater good.

The coincidences in “The Promise” are too frequent. (Chris and Ana and Michael, or some combination thereof, always seem to be able to find each other, even in the midst of utter chaos.) The melodrama is a little too heavy-handed at times. And for a movie that clocks in at 134 minutes, all of a sudden it feels as if we’re rushing through the conclusion and to a touching epilogue that might have been even more effective had it been given a little more real estate.

Yes, “The Promise” veers into corny territory, and yes, it’s derivative of better war romances — but it’s a solid and sobering reminder of the atrocities of war, bolstered by strong performances from Isaac and Bale, two of the best actors of their generation.

★★★

Open Road presents a film directed by Terry George and written by George and Robin Swicord. Rated PG-13 (for thematic material including war atrocities, violence and disturbing images, and for some sexuality). Running time: 134 minutes. Opens Friday at local theaters.