The assassination of Austrian Archduke Franz Ferdinand on June 28, 1914, was the flashpoint that started a catastrophic chain of events.

It set the crumbling Austrian-Hungarian Empire on a collision course with Serbia, dragging Europe into World War I, which in turn led to World War II.

Now a new theory suggests a humble sandwich was to blame for the whole lot.

Historians believe the Archduke’s killer, 19-year-old Gavrilo Princip, stopped for lunch before committing the fateful deed outside a delicatessen called Schiller’s.

They suggest if he hadn’t stopped to snack where he did, he would never have been in the right place to shoot Ferdinand.

“No sandwich, no shooting. No shooting, no war,” Mike Dash summed it up succinctly for the Smithsonian magazine.

Dash said as far as he can tell, the theory first began circulating in 2003, and has been gaining more and more traction ever since.

However, while it’s a good tale, he said there are a few holes in the story.

“It simply doesn’t ring true,” he wrote.

“That’s not because the modern version isn’t broadly faithful to the facts; it’s not even utterly implausible that Princip might have stopped for a bite to eat.”

“No, the problem is that the story is suspiciously neat — and that the sandwich is a quintessentially Anglo-American convenience food.”

“I find it hard to believe the sandwich would have featured on a Bosnian menu as early as 1914.”

He suggested instead as far as he could tell, the rumor sprang from a British-made documentary called “Days that Shook the World.”

About five minutes in, the script stated: “Gavrilo Princip has just eaten a sandwich, and is now standing outside Schiller’s delicatessen … Completely by chance, fate has brought the assassin and his target within 10 feet of each other.”

The documentary’s writer, Richard Bond, reportedly told the Smithsonian that his meticulous research included resources in a number of languages, and said: “It’s possible that ‘sandwich’ was a colloquial translation that appeared in these sources.”

According to a fact check in Thewrap.com, the coincidences continue.

Phil Hornshaw writes one of the seven would-be assassins hoping to kill the Archduke screwed up an attempt to blow up his car with a grenade.

The fuse reportedly burned so long that it bounced off the vehicle, dropping onto the ground and injuring soldiers while Franz Ferdinand escaped unscathed.

The incident forced him to divert from the original route his motorcade was taking through Sarajevo, and then he got lost.

He was reportedly hoping to make his way to a hospital to meet his injured men when the motorcade found itself at Schiller’s.

Somehow, he popped out back on the original route, lining up perfectly with Princip’s prime position outside the delicatessen.

Since all the major details of the storyline up with historical accounts, there is some plausibility to the theory of the assassin’s lunchtime snack.

But let’s be real: he probably didn’t eat a sandwich at Schiller’s.