“In any martial arts fight, there is only a finite amount of ninjutsu available to each side in a given encounter. As a result, one Ninja is a deadly threat, but an army of them are cannon fodder.”

From the TvTropes page.

This is one of those tropes that I think is as well known and wide-spread as the Training Montage, but most people probably didn’t realize had a name.

You see the Conservation of Ninjitsu all the time in books and movies. The hero wades through countless mooks (henchmen, ninjas, stormtroopers, zombies, pirates, you get the idea), but then they get to one bad guy. You know the one—this one isn’t wearing a helmet, they’re a giant, they’re wearing badass armor, or have some other defining features that set them apart from the rest of the nameless bad guys that litter the ground. 

Now our hero is stuck in a fight to the death. What makes this one ninja different from all the rest?

Remember in The Matrix how it was basically certain death to fight an Agent one on one? Then in the sequels (ignore how you feel about them) Neo and the gang are fighting dozens of Agents at a time? 

What gives?

That’s the idea behind today’s trope. 

There’s a couple factors at play: One is anonymity, which in fiction does not help survival. The other factor is dramatic tension. 

Let’s take these one at a time. 

What does our lone hero (or team) have going for them that the army of faceless ninjas or soldiers doesn’t have? The correct answer is backstory. 

See, it takes a lot of time to get readers and viewers invested in a story and in its characters. It’s serious business to kill off a main character that readers are invested in. It’s not something that readers or (most) authors take lightly. 

But what if someone has to die to advance the plot or give our hero a much needed reason to go on that Hero’s Journey? Remember grandma or that kind uncle? They only had one scene, so we readers don’t really know them all that well, but man was man was that scene heartfelt and it showed how much they mean to the main character. Guess who’s dying in the first act? If you guessed grandma or the kind uncle—good job. 

Most of the time you can get away without killing any main characters at all, provided there’s a few side characters for cannon fodder. 

This phenomenon of backstory and survivability is why those singular bad guys—you know, the ones that don’t wear helmets or maybe they have an awesome sword—survive when so many other of their faceless comrades don’t.

There’s an old Star Trek joke about Kirk, Spock, McCoy, and Ensign Ricky going down to a dangerous planet. One’s not going to make it back. Poor Ricky got a name, but forgot that ever-important backstory. 

This is also part of the reason that the Big Bad Evil Guy can stand up against an onslaught from a team of heroes. He (or she) has the power of backstory! 

This hypothetical fight between the BBEG and the team of heroes brings us to our second factor in today’s trope: Dramatic Tension. 

Let’s back up slightly to our original picture: Our hero surrounded by hundreds of ninjas. Right away, being outnumbered is giving the scene dramatic tension. It evokes the question of if they’ll survive. 

Conversely, if our team of heroes is fighting one lone BBEG, we know that villain is so badass that they’re going to put up one hell of a fight. This also evokes the question of if they’ll survive. Even if the heroes win, they might have to win at some great cost. 

 So, there’s your breakdown of the Conservation of Ninjitsu. Do you recognize this trope from any of your favorite media? Does it play into any of your favorite scenes? Have you used it in your own writing?