So You Want To: Write An Alien Invasion Story

One of the oldest subgenres of science fiction is the alien invasion. Monsters from another planet come to Earth to eat our brains/mine our planet/terraform and colonize the Earth. If you're looking to write an alien invasion story, keep reading.

Necessary Tropes

Military and Warfare Tropes are useful when writing about an invasion. Alien Tropes are the other half of it.

Choices, Choices

You'll want to put some thought as to the scope of your story. How many aliens are arriving? Stories have revolved around entire armies (Battle: Los Angeles) and sole survivors (E.T.). Additionally, there's the question of how much of the invasion you're going to depict. The Red Dawn films may involve a large-scale invasion of American soil by foreign powers, but mostly focus on one cell of The Resistance, with little news about the rest of the country getting in or out.

What are your aliens like? And, perhaps more pertinently, why are they here? The thing about invasions is that they aren't done for shits and giggles. Basic military strategy: you invade and occupy a region because it has something you want. If aliens are coming here, from godknowshowmany light-years away, it's because there is something valuable on Earth. What is it? Why is it valuable to them? That's going to dictate a lot of things, like their military and occupational strategy, and intersect with the idea of "alien" (IE superior) "technology" in a lot of interesting ways. For instance, if the aliens are Planet Looters and just here for our water, there's no reason they necessarily have to mount an armed invasion at all: just park a giant tanker ship in the middle of the ocean and turn on the vacuum hose. The first thing any humans would know about it is when the sea level started dropping, and it would do so in such a gradual fashion that it might take years for anyone to notice. (Observe how long it's taken us to notice the sea level rising due to climate change. It's been so gradual that some humans still deny that any such thing is happening.)

What kind of aliens are we talking about? Rubber-Forehead Aliens are played out, but Starfish Aliens can be impossible to write. Obviously, you'll want to strike a balance between the two, but what is your exact balance? What is the biology of these aliens? There are many, many amusing little twists of physiology you could play. Ever messed around with the chirality of proteins? Mass Effect did, to very interesting effect.

A really interesting question: when is this going to happen? Traditionally these stories take place In The Present Day, or occasionally Twenty Minutes into the Future (Enders Game), but what about the past? We've already had Cowboys Vs Aliens. How about Knights In Shining Armor vs Aliens? Cavemen Vs Aliens? Wooden Ships and Iron Men Vs Aliens? Five Races Vs Aliens? Plenty of schlocky action movies, and maybe even some good stories, lie waiting to be discovered here.

There are questions of tone to consider. An Alien Invasion story is science-fiction, which makes it subject to the Mohs Scale of Science Fiction Hardness. How realistic, or at least "consistent with our current understanding of science," do you want your work to be? You don't need to have perfect consistency; Battle: Los Angeles handwaves most of the tech but has very authentic military operations, with the invaders utilizing the same sorts of strategies and tactics that humans would in the same situation. Conversely you have Independence Day, which was frankly ridiculous on all levels but made a lot more money.

And there are questions of tone to consider. In Real Life, any alien species that found Earth and decided to mount an offensive operation would probably possess technology indistinguishable from magic, and be able to conduct a planet-wide Curb-Stomp Battle with ease. So how realistic do you want to be? True, there might be an Achilles' Heel somewhere in the alien army (say, a thermal exhaust port two meters wide), but how likely is it that the aliens have overlooked it all this time, or that their previous victims never found it? You may need to do some serious juggling to make this work.


The Mohs Scale is a big one here. According to our current understanding of science, Faster-Than-Light Travel is impossible; there are laws of physics preventing it from occurring. So either you're going to break the laws of physics or you're going to have to put a lot of planning and preparation into the alien army. Remember how much work it was for Earthers to put a man on the Moon? Well, imagine putting an invading army on a planet which is about a gazillion times further away from us than the Moon is. The monetary expenditure alone would be, well, astronomical. And you'd need to do your absolute damnedest to make sure 1) the soldiers survive the trip, and 2) the soldiers survive the fighting on the other side, at least long enough to accomplish their mission. Imagine spending $19 trillion on an interstellar mission only to find that the planet's atmosphere is made of magically-anti-Homo-sapiens chemicals and that all the soldiers simply melt upon opening the hatch. Well, as the mission planner (or rather, The Author), it's your job to imagine those things, and make sure your soldiers don't fall victim to them.

You also need to make sure the whole invasion is for logically plausible reasons. To repeat, an invasion is the military outcome of political or economic desires: "Over there, they have some sort of Unobtainium, and we want it, and the best way to get it is to take control of the region by swordpoint." An entire period of world history, Colonialism, was driven by this desire, meaning that a lot of modern consumers—or, at least, those who have taken History classes—know something about the hows and whys of what your aliens are trying to do. Make sure their tactics pass muster to those with a high-school education.

Potential Subversions

One big subversion is to turn the tables emotionally. One of the advantages of an Alien Invasion story is that the defenders—human beings—almost automatically have the audience on their side, because they (the audience) should be able to see themselves in the defenders. But why are the invaders invading? And what happens if they lose? Tales of Phantasia, essentially a fantasy version of an Alien Invasion story, pulled a massive Plot Twist by revealing that the Big Bad, Dhaos, had invaded to secure precious resources (mana specifically), without which his world would wither and die. Though he became a Well-Intentioned Extremist along the way (the humans of Phantasia had begun too wreak ecological havoc with Magitech, and he decided to wipe them out), the heroes acknowledged that defeating him didn't necessarily make them good people, and that they were condemning the citizens of this other world to death by saving their own. (Fortunately, a Deus ex Machina helped elevate the emotional tone of the ending.) Most Alien Invasion stories are very clear about the consequences if we humans lose, but what are the consequences if we win?

This leads into the next potential subversion: do military conflicts always have to be solved militarily? Humans have always hoped that it would be possible to coincide peacefully with sentient creatures from other planets, and if these aliens are here for something on Earth, they must have something similar to us. Maybe peace is possible, if people with calm heads (from both sides of the war) manage to get in contact with each other. Timothy Zahn's The Conquerors Trilogy revolves largely around this, albeit in a Space Opera background. You have to be desperate to launch an unprovoked invasion of someone else's homeland, as opposed to the minor military skirmish which starts off the war in Conquerors Trilogy. Of course, this desperation may prove useful when it comes time to hit the negotiating table. Consider taking a brief look at the Orson Scott Card work Speaker for the Dead, sequel to Enders Game, which doesn't focus a lot on his gay politics and instead talks about Inscrutable Aliens and the line between them and, well, non-inscrutable aliens.

Writers' Lounge

Suggested Themes and Aesops

There are plenty of Green Aesops to be had here. If Planet Looters are taking the effort to go ga-trillions of miles out of their way and invade our little blue planet, they've probably already wrought ecological hell on their own homeworld. There's definitely an anvil to be dropped there.

Potential Motifs

Suggested Plots


Set Designer / Location Scout

Just about anywhere on Earth, when you get down to it. Hell, one crazy filmmaker had his aliens popping out of the deepest part of the ocean!

Props Department

Costume Designer

Casting Director

Stunt Department

Extra Credit

The Greats

The Epic Fails