Apparently, the real St. Nick wasn’t always so jolly.

In 325 CE, Roman-occupied Turkey played host to a meeting that ranks among history’s most significant: the First Council of Nicaea. Back then, Christianity as we know it was merely a fledgling religion enjoying a rapid spike in influence. But not all early Christians were on the same page: Jesus’ divinity became an especially polarizing issue. Certain factions believed that he wasn’t fully divine while others (to put it very, very mildly) strongly disagreed.

Seeking unity, Emperor Constantine I (ca. 285-337 CE)—who would eventually convert via deathbed baptism—summoned hundreds of bishops with various theological stances to a month-long gathering at his Nicaea vacation home. Among the ruler’s esteemed guests was one Nicholas of Myra, a future saint who’d already acquired regional fame for showing generosity towards impoverished locals.

Also in attendance was the controversial Arius (250-336 CE). His position that Jesus was lesser than and subservient to God didn’t exactly make him the event’s most popular guy. Nicholas, like many, harbored a strong disdain for Arius’ convictions, but largely managed to keep civil. However, legend has it that one fateful day, St. Nick’s patience finally ran dry.

What went down, exactly? The details are unclear, but according to Damaskinos of Athens (a twentieth-century archbishop and armchair historian), “The emperor was sitting on his throne, flanked by 159 bishops to his left and 159 to his right. [Arius] was presenting his views with great vigor and detail. As Saint Nicholas observed the scene, the emperor listened in complete silence and without interrupting this discourse. Outraged, and prompted by his saintly vigor, he walked up to Arius, faced him squarely and slapped his face.”

Different versions of this story—including several retellings wherein Arius gets punched out cold—have been circulating for the better part of 1700 years, though not all academics agree that their violent showdown actually happened. Nevertheless, artists have long-since immortalized St. Nicholas’ smack heard ‘round the world, a rumble you can even see painted inside Turkey’s beautiful Sumela Monastery.