Today’s Wonder of the Day was inspired by Caiden. Caiden Wonders, “What are the History of Ninjas” Thanks for WONDERing with us, Caiden!

As you're sleeping one night, your sweet dreams are suddenly interrupted by an unwelcome visitor. A mysterious masked man clad in black appears behind you. You take off running. You turn here and there but he's always behind you, moving quickly without a sound.

You catch only glimpses of your pursuer. It looks like he has a long sword strapped to his back. You don't know who he is, but you know you must not be caught. Another turn and you run the length of an alleyway only to be met by a tall wooden fence. Is this the end?

You hear thuds on each side of your head. Sharp, star-shaped pieces of metal have lodged themselves into the wood near your ears. You turn to face the man in black, who now has his sword drawn. As he raises his sword, he jumps into the air and extends his leg in a karate kick aimed at your head when…you sit up in bed, breathing heavily. Whew! It was just a dream.

Now that you're awake, you know who your attacker was: a ninja! All the tell-tale signs are there: all-black clothing, stealth, sword, throwing stars, and martial arts — definitely a ninja!

Ninjas are popular characters today. Kids dress up as ninjas for Halloween. Ninjas populate movies, television shows, and books. The word ninja even comes up in the context of teenage mutant turtles, kitchen blenders, and motorcycles. But are ninjas even real?

If you're a fan of ninjas, you'll be pleased to know that ninjas were indeed real. However, the real ninjas of the past were probably nothing like the modern version of the ninja you're familiar with.

Unfortunately, historians have not been able to piece together a very reliable picture of what the true ninjas of the past were like. There remains much debate amongst scholars about who the ninjas were and what they did. This confusion is a natural result of the fact that ninjas were spies who led very secretive lives.

Most scholars believe ninjas were specially-trained covert agents who lived during Japan's feudal era. Although their predecessors could have appeared as early as the 12th century, ninjas are associated primarily with the tumultuous times of the Sengoku period in the 15th-17th centuries.

Ninjas were known to inhabit two specific areas in the heart of central Japan: Iga and Koga, which are known as Mie and Shiga prefectures today. Similar to Appalachia in the U.S., these remote areas were largely undeveloped and sparsely populated. Filled with rolling hills, thick forests, and deep valleys, the land in Iga and Koga wasn't as suitable for farming as other areas.

While surrounding areas were filled with warring samurai, the villagers of Iga and Koga determined to stay free of warlords. To that end, they trained people in the art of ninjutsu.

Unlike traditional martial arts, like karate, ninjutsu concentrated on a specialized set of skills. Rather than hand-to-hand combat, ninjutsu skills included stealth, gathering intelligence via espionage, and undermining an enemy via strategic activities such as infiltration, sabotage, and assassination.

The term ninja comes from the Chinese language and didn't appear until the 20th century. In feudal Japan, ninjas were known as shinobi, which meant man of perseverance and stealth. Unlike samurai, who were born into their social class, shinobi referred to a profession.

Some scholars see the samurai and shinobi as opposites. Samurai were honorable warriors who fought openly, whereas as shinobi acted in secret and used dishonorable methods. These scholars believe the shinobi were largely villagers from Iga and Koga who fought covert operations against the samurai warlords to maintain their independence.

Other scholars believe the shinobi were actual samurai who had been defeated at one time or another. They trained to become shinobi and then acted as mercenaries who hired out their services to other samurais.

Whatever their exact lineage, it's clear that the shinobi acted as covert spies and professional warriors trained in stealth tactics and guerrilla warfare. Although it's unclear whether the shinobi ever used throwing stars as weapons, they did likely rely on a vast array of specialized equipment and weapons, including explosives, fire, poison gases, swords, knives, bows, ropes, ladders, and grappling hooks.

What about those masks and all-black outfits? Those are a modern creation. The shinobi would've worn common clothing that helped them blend in wherever they were, rather than an all-black outfit that would've made them stand out from the crowd.

The shinobi faded away after the unification of Japan in the 17th century. Over the following century, the mystery of the shinobi tradition became popular in the imaginations of the Japanese.

Legends and myths abounded about the shinobi, including fanciful tales of special abilities, such as invisibility and walking on water. Our modern version of the ninja is mostly based upon these old legends and myths rather than the true, historical shinobi that existed during the Sengoku period.

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Tomorrow’s Wonder of the Day may cause you to do a double-take!