15 Times a Simple Mistake Changed the Course of History
History is often shaped by grand plans and powerful leaders, but sometimes, it’s the little mistakes that change everything. A missed signal, a wrong turn, or a bad decision in the moment has altered wars, shaped nations, and even created inventions by accident. These surprising stories prove that even the smallest errors can leave a giant mark on the world.
- Tricia Quitales
- 4 min read
Not all turning points in history came from battles or bold ideas — some were the result of human error. From tiny oversights to misunderstood orders, simple mistakes have triggered wars, toppled empires, and changed daily life forever. While some of these errors were tragic, others led to unexpected breakthroughs. Explore 15 moments where one wrong move rewrote the past.
1. A Missed Telegram Helped Start World War I
Carl Pietzner on Wikimedia
After the assassination of Archduke Franz Ferdinand, a critical telegram meant to ease tensions was delayed. Without the message, Austria-Hungary pushed ahead with threats. That simple delay helped launch one of the deadliest wars in history.
2. Napoleon’s Invasion of Russia in Winter
Andrea Appiani on Wikimedia
Napoleon underestimated the Russian winter and delayed retreating. His army froze and starved, with hundreds of thousands dying. A poor timing mistake destroyed his dream of controlling Europe.
3. A Wrong Turn Led to the Assassination of Franz Ferdinand
Achille Beltrame on Wikimedia
The Archduke’s driver took a wrong turn in Sarajevo and stalled near a café. A waiting assassin saw the chance and took it. That gunshot directly led to World War I.
4. NASA’s Metric Mix-Up Caused a Space Crash
NASA/Ken Ulbrich on Wikimedia
In 1999, the Mars Climate Orbiter crashed because one team used metric units while another used imperial. The spacecraft burned up in the Martian atmosphere. A simple unit mismatch cost $125 million and a major mission.
5. A Translation Error Caused the Atomic Bombing of Hiroshima
George R. Caron / Charles Levy on Wikimedia
Japan’s response to a U.S. surrender request used the word “mokusatsu,” meaning either “no comment” or “ignore.” The Allies took it as a refusal. Days later, the bomb dropped on Hiroshima.
6. A Sleeping Guard Lost Constantinople
anonymous on Wikimedia
In 1453, a tired guard forgot to lock a small gate in the city wall. Ottoman soldiers found it and rushed in, capturing the city. A tiny oversight ended the Byzantine Empire.
7. A Storm Saved England from Invasion
Creator:Oswald W. Brierly on Wikimedia
The Spanish Armada was ready to invade England in 1588 but made a navigational error during a storm. The ships scattered, many wrecked on rocky shores. Bad weather and bad planning saved England from conquest.
8. The Challenger Disaster: O-Ring Overlooked
NASA on Wikimedia
Engineers had concerns about O-rings in cold weather, but the shuttle still launched. The faulty part failed, and the shuttle exploded, killing seven astronauts. It was a tragic mistake born from pressure and miscommunication.
9. Cleopatra’s Suicide May Have Been Based on False News
William Wetmore Story on Wikimedia
Cleopatra believed Marc Antony had died in battle, but he hadn’t. Heartbroken, she killed herself — and Antony followed after learning the truth. A mistaken report ended both their lives and Egypt’s independence.
10. The Titanic Ignored Ice Warnings
Anonymous on Wikimedia
Radio operators on the Titanic dismissed iceberg warnings as non-urgent. That mistake contributed to the ship hitting an iceberg and sinking. Over 1,500 people died from avoidable errors.
11. A Misspoken Command at Gettysburg Lost a Key Hill
Civil War Glass Negatives on Wikimedia
Confederate General Richard Ewell was told to take Cemetery Hill “if practicable.” He hesitated, thinking it wasn’t urgent. That hill became a stronghold for Union forces and helped turn the battle.
12. A Napoleon Army Attack Was Based on the Wrong Time
Bonhams on Wikimedia
At the Battle of Waterloo, Napoleon’s generals attacked later than planned. Their watches were off by hours. That delay gave the enemy time to reinforce, leading to Napoleon’s defeat.
13. A Wrong Button Almost Started World War III
Stanley Scott Collection on Wikimedia
In 1983, a Soviet officer saw what looked like a U.S. missile attack on his radar. He chose not to report it, thinking it was a glitch. He was right, and his calm decision may have saved the world.
14. Alexander Fleming Didn’t Clean Up—And Found Penicillin
Calibuon on Wikimedia
Fleming left the Petri dishes out while on vacation. When he returned, he noticed mold killing bacteria. That mistake led to the discovery of antibiotics and saved millions of lives.
15. A Farmer Burned His Field and Found Pompeii
Jebulon on Wikimedia
In 1599, a builder digging for water stumbled on ruins but thought it wasn’t important. He moved on, leaving the discovery forgotten for centuries. It wasn’t until 1748 that Pompeii was truly unearthed.