One of the most consequential loopholes in history didn't involve laws or taxes, but wine cups. This simple trick may have saved all of Europe from conquest.
In the early 13th century AD, Ögedei Khan, the son of the legendary Genghis Khan, ruled over the vast Mongol Empire. While a capable leader, he had a severe weakness for alcohol.
His drinking became so worrying that his brother, Chagatai, intervened. He tried to get Ögedei to swear off alcohol, but when that failed, he managed to limit him to a certain number of cups per day.
But Ögedei found a clever way around the rule. He agreed to the limited number of cups, but then had special, oversized cups made so he could drink just as much as before.
This habit continued unchecked. On a winter night in December 1241, after a long bout of drinking with a companion, Ögedei Khan died at the age of 55.
His death couldn't have come at a more critical moment in world history.
Mongol armies, under the command of General Subutai, were at that very moment sweeping through Europe. They had crushed Polish and Hungarian forces and were poised to push deeper into the continent.
However, Mongol law dictated that all princes of Genghis Khan’s line had to return to the capital to elect a new Great Khan. The invasion of Europe was immediately halted, and the armies turned back.
They never returned. A simple, stubborn act of defiance, born from one man's vice, altered the course of history for an entire continent.