Everybody knows about Archduke Franz Ferdinand.

He has catchy alliteration, there's a band named after him, and he's the answer to a question in every single trivia game created in the last 100 years. He got shot, he died, and it kicked off this little thing we call World War I.

Except it wasn't a world war yet.

Ol' Ferdi's assassination started the war in Europe. But, Shmoop helpfully points out, one continent does not a world war make. So, no Alex Trebek, "Who is Franz Ferdinand?" did not start World War I. His assassination only started a chain of events that would eventually become a world war after a lot of other nations joined in.

When Franz was assassinated, the U.S. couldn't have cared less. Europe was a hot mess that Americans wanted nothing to do with. Some rich Archduke in a silly hat got shot while driving around in a city far, far away, and for some reason that started all the Kings, Queens, and miscellaneous European leaders trying to kill each other. It was Game of Thrones with machine guns. Entertaining? Yes, if you're into gore. But not something you'd want to be in the middle of. Americans were happy to watch from the safety of another continent as Europe tore itself to pieces for two-and-a-half years.

Until the U.S. got sucked in, too.

Arthur Zimmermann was the German Foreign Secretary who had a really bad day at work in January of 1917, and who, with one telegram, did exactly the opposite of what he was supposed to do: got the U.S. to declare war on Germany. The telegram was a top-secret, coded message urging Mexico to attack the United States. Thanks to the crack cryptographers in the British Navy's intelligence service, it was intercepted, deciphered, and published where the American public would read it and be so shocked and appalled that they were willing to support a war they once wanted nothing to do with.

As far as workplace screw-ups go, this one was top notch. So next time you get asked, "Who started World War I?" impress your friends and say, "Arthur Zimmermann." It doesn't have quite the ring of a certain Archduke, but it's just as accurate. Zimmermann is the guy who got the U.S. involved and actually made it a world war as opposed to just another war between European monarchs who were all cousins by marriage anyway.

Have you ever had a teacher who hated it when students passed notes in class? Like, they would get all upset and offended, and make a big production about taking the note away and reading it in front of everyone.

Come on. Who cares? It's just a note.

It's not like a note could start a war or anything. Notes don't kill people. Notes don't make armies cross oceans to slaughter other armies. Notes can't redraw world boundaries creating new nations and erasing others. No one ever became a world superpower because of a little note.

Oh, wait.

The Zimmermann Telegram was a note that did kinda do all that.

World War I, "the war to end all wars" (wishful thinking, we guess), reshaped Europe and marked the emergence of the U.S. as a major world power. We take that for granted today, but before WWI, Europe was large and in charge.

As a result of the war, the large, multinational Austria-Hungarian and Ottoman Empires were dismantled as their national minorities demanded self-determination; boundaries of newly created, smaller countries like Finland, the Baltic states, Iraq, Syria, Czechoslovakia, and Yugoslavia, redrew the map of Europe. The former Ottoman Empire in the Middle East was arbitrarily carved up by the Sykes-Picot Agreement into areas of French (Lebanon and Syria) and British (Iraq, Palestine, and Jordan) control.

Did those countries have any say about it?

Hint: No. We're still paying the price for that today in the Middle East.

Germany was stripped of territory, disarmed, humiliated, and economically devastated—a situation that set the stage for a guy named Adolf Hitler to whip up nationalist anger and provoke World War II. Russia replaced their czarist autocracy with a communist government and China soon followed suit. A modern world emerged, where universal suffrage, freedom, and national self-determination replaced 19th-century imperial domination. President Woodrow Wilson established a League of Nations (that eventually morphed into the United Nations) that he hoped would secure a lasting peace. Good luck with that.

In short, everything changed.

As one writer wrote in 2014 on the 100th anniversary of the beginning of the war,

We should not see [the war] merely as something of historical interest, a series of sepia photographs showing people who are quite alien to us. We are still living with the results of that war, and we face similar concerns. How, for example, does the world deal with powers whose leaders feel they must have their place in the sun? For Germany then, read Russia now. Or how can we rebuild societies after deeply damaging conflicts—in Europe then, but in Central Africa, the Middle East or Afghanistan today? (Source)

All that because of one note.

The takeaway? Sometimes in history, it's the little things that count.