They started a war in 15 minutes.

At 1:43 p.m. on Aug. 19, Bruno Cardinali , a marketing executive for Popeyes Louisiana Kitchen, got a WhatsApp message from a colleague: That morning, one of Popeyes’ fast-food rivals, Chick-fil-A, had tweeted what appeared to be a thinly veiled critique of the new fried chicken sandwich that Popeyes had started offering nationwide a few days earlier.

Mr. Cardinali quickly convened a group of marketing officials in a small room on the fifth floor of the Popeyes headquarters in Miami. A high-speed brainstorming session ensued, and before long, the team settled on what seemed like the perfect response: “... y’all good?”

The tweet appeared on the official Popeyes account at 1:58 p.m.

“It was 15 minutes of turnaround putting out the tweet that triggered the whole thing,” Mr. Cardinali said. “And at that moment, we braced ourselves.”

What the tweet set off were the “chicken sandwich wars,” a viral social media debate that has captivated the internet for the last week and a half. Popeyes, Chick-fil-A and other fast-food brands traded barbs on Twitter, arguing about whose sandwich tasted best. As sandwich memes proliferated, customers flocked to Popeyes restaurants across the country, forcing employees to work hours of overtime as location after location sold out of the sandwiches.