Any that is realistic — and, by ‘realistic’, I mean, they way we might do it.
Imagine you buy a property and, while surveying the grounds, you discover a wasp’s nest in the barn. How would you get rid of it?
Would you make a lot of noise, and get into combat, taking aim and shooting each wasp out of the air, one by one, all the while taking stings as they defended themselves, and missing enough to essentially destroy the structure that’d you only have to clear and rebuild?
Nah. You’d likely wait till evening when they’re tucking themselves to sleep; use some smoke to incapacitate them, and then use some chemical to kill them all. There’d be no fight. You’d just use your intelligence to minimize the chances you’d even get stung while you eradicate them all in one smooth operation, clear their carcasses out of the way and use the barn you bought with the property.
But, a movie like this would be over before the opening credits, right?
Movie makers need to tell stories that can take 90 minutes of our time, stories in which some aliens with obviously far superior intelligence and technology travel from who knows were all the way to our little blue marble…make a big production of arriving, and then get into a fight with us. And we prevail!
Balderdash. We wouldn’t see it coming, and it’d be over before we knew what hit us.
EDIT: Two things: first, THANK YOU to all who’ve found this answer interesting enough to upvote, and/or engage in conversation! Second, I recently heard that, apparently, signs of life were detected on Venus…if indeed such is the case, well, then, we now know aliens do exist, and WE ARE the aliens! (at least from the vantage of whatever constitutes life on Venus).
The chisel:
Scientists detects an extrasolar asteroid, with a shape that resembles Oumuamua but far larger, far denser, and approaching with a speed far greater.
The only difference is the strange haze of tinier objects that follow it.
Its tractory passing close to our sun, but nowhere near Earth, makes no alarm bells ring.
Astronomers are watching in anticipation as it makes its close pass. As it passes strange outgassing makes it change its course, and to the horror of the bywatchers they now realize that it is on a dead-on collision course with Earth … Far too precise to be a coincidence!
With less than 2 days to impact, there is nothing to do.
A tiny part of the asteroid breaks free seconds before the impact, blowing a hole in the atmosphere, and softening the bedrock. As the asteroid hits the ground and disappears like a springboard diver, firestorms rage, and earthquakes shake the surface, Humanity wonders if that was all?
Little do they know that the “asteroid” continues its journey through the layers of the earth, hitting the core minutes later. The vast explosion of the collision is dampened by the crushing gravity, but the core is now in motion out through the layers. As the crushing gravity diminishes the core changes from being solid to liquid to gaseous metal until poor Earth spews out its innards into the universe in a giant explosion.
At this point, the “haze” of self-replicating machines arrives at the scene. Settling at the trillion of still glowing pieces of the core, and preventing them to fall back at the remainder and form an earth version 2.0.
200 years later the aliens arrive, long-lived water creatures, perfectly fitted to a life in 0 G, expecting to start building their waste structures of the “newly” harvested metal. Imagine their surprise when they encounter the small Mars colony of humans struggling to survive at their run-down base.
They are understandably truly sorry, have no explanation for how they could have missed a developed species when their drone ships visited 12000 years ago, and generously offer 10% of the spoils, plus help to construct space habitats for the remainder of the human race … But they are equally puzzled by the animosity they are met with, after all “You can’t make an omelet, without cracking some eggs”
The strategy depicted in the movie The 5th Wave was quite terrifying. It was also very smart and efficient on the aliens part.
- Knock out all electricity using EMP
- After some time, cause earthquakes and tsunamis to kill off most people.
- After some time, cause a deadly pandemic and kill off even more people.
- Send down a few aliens posing as human military and kill off as many of the remaining adults as possible
- Brainwash the surviving kids to join the military and get them to attack any remaining adult survivors. In effect, get the last remaining humans to kill each other.
That’s a very smart alien strategy. They’re not hard up to just land on the surface. They have a pragmatic strategy which puts no aliens at risk for the first three waves, and puts minimal aliens at risk for the 4th and 5th wave. Their extermination strategy is also environmentally friendly, preserving the earth they aim to conquer rather than bombing or nuking it and rendering it unliveable even for them.
While pragmatic for them, for the humans it’s a long drawn out misery of calamities, a slow and terrifying death largely by disasters, culminating in a plan for them to kill each other off.
The Combine dystopia as seen in the Half-Life Series.
Absolute capitulation, irreversible transformation and the withering away at any and all facets of individual expression and choice.
In George Orwell’s 1984 only the proles are allowed to exist in the periphery of the party’s (Ingsoc) sight, all information, narratives and even the formulation and expression of individual thought is contorted to the Party’s needs. If the party says 2 + 2 = 5 then it has always been so, and if it is 3 the next day, the same holds true.
(Stalker – Half-Life 2)
In the Half-Life universe, the Combine is a mysterious intergalactic and even interdimensional form of Ingsoc, an alien race so powerful that its invasion of Earth lasts but seven mere hours.
What they proceeded to do with their newly conquered planet and its cognizant apes potentially explains the Fermi paradox: Why does no other intelligent species seem to be making any such noise as we are?
Maximum civil distortion
What remains of humanity after a school day’s passage is rigorously stripped of any capacity to form relationships.
Family units are disbanded and people are constantly relocated from city to city so that they are —always— surrounded by strangers in an unfamiliar environment. In Half-Life 2 you encounter a woman who’s grateful for being allowed to stand beside the platform. She tells you that they stopped her train in the middle of the woods just to take her husband off.
Evidently, a mistake in bureaucracy led to two persons of intimate relations end up on the same transport, the implications don’t bode well.
(City 17 Citadel Half-Life: Alyx — a bio-robotic superstructure under construction)
The final generation
Everything is sanctioned, living space, people, “food”, keepsakes and even coherent memories as per the tailored water supply.
Across the entire planet, the combine has established a suppression field which prohibits embryonic development – reproduction is rendered impossible and humanity will die out within 80 years. “non-mechanical stimulation” as it is called, is reserved for humans in the ranks of Civil Protection; a genocidal police force in which the reward for joining is improved rations and the penalty for failing to “neutralise” an entire apartment block, that has one unaccounted person residing within?Well, that’s ++ungood for you and your “family cohesion”.
Yes, you’re permitted to see your family if only you join the steroid-suit Gestapo, stifle the dying embers of human self-determination, and don’t disgruntle the coded Overwatch Voice.
(Half-Life: Alyx — CPs conducting an irregular sweep of a sector)
Depersonalisation and global pillaging
The Combine does not have a notion of humanity as an entity separate from itself, rather, it—and the entirety of the human race—is one singular organism along with all the other alien species it has enslaved. This is echoed in the unnerving manner in which rebellious citizens are referred to as simply “malignant” by the aforementioned voice.
If you act with any greater autonomy than a red blood cell, you are a cancerous growth that must be destroyed immediately /or/ made a terrifying example of. The stalker in the first pic is a human who has undergone drastic physical and cybernetic alteration, processed into a mindless servant of the citadel, they have no vocal cords, no digestive tract, no reproductive organs and no sense of self.
Only the protagonist Gordon is ever called “Individual”.
(Alyx’s marked globe. An annotated antique map—probably the only ones not to be destroyed—shows the utter confusion of what even an ‘educated’ citizen manages to fathom about Earth’s state, some 15 years after the Combine invasion)
The Combine terraform and excavate deep into the earth without any regard for the environmental consequences. Water is exported off-world leading to inhospitable desserts, widespread ecological catastrophe and vastly diminished sea levels.
The numerical cities dotted around the earth are the only significant settlements left and arguably the only ones fit for human habitation of any kind. Even if the humans manage to fight back successfully they’ll have little means of independent sustenance, in a wasteland of a world.
Horror doesn’t begin to put it right. The Combine are a representation of what a highly advanced species could do to a lowly order like type 0.8 Earth if ever they chose to exert themselves as such, and it’s all without the mention of the invasive and infectious flora and fauna that accompanied their arrival.
