Inspired by these two questions here and here that contemplate similar issues, I’m now interested in finding the best strategy for defeating (not destroying) another planet.

The year is 2390. Humanity has taken to the stars and achieved interstellar travel. Humans now inhabit eleven planets in four different star systems. While most of these planets required sophisticated and expensive techniques to colonize (too frigid, barren, or hot to otherwise support human life naturally), two planets are beautiful terran-style worlds. One is Earth, and the other is (for the sake of this question) New Earth.

Sadly, diplomatic relations between these two planets have been souring for several decades and recently exploded into all-out war. Unfortunately for Earth, New Earth’s space fleets were much better prepared and have essentially annihilated Earth’s entire space-faring navy. At this point, Earth and its five billion inhabitants are now severely vulnerable, but can certainly continue to build threatening ships and anti-orbital defenses on the ground. As a result, they have not surrendered.

New Earth wants to ensure that Earth’s citizens are unable to pose a present or future threat to its new space empire while minimizing the cost to themselves. What is the best strategy to accomplish this?

Bonus Objectives

The most obvious solution to this problem is to simply start pushing (or dropping) moderately sized asteroids into the atmosphere. This is certainly a quick way to guarantee victory, but violates the following bonus objectives that the New Earth navy is hoping to fulfill with their strategy:

  • Earth-like planets are rare, so destroying the planet is not an option.
  • For the same reason, mass-extinction events that make the planet unsuitable for human habitation is not an option.
  • Massive loss of civilian life should be avoided if possible. It won’t look good on the news at home if millions of innocent people die.
  • New Earth wants an unconditional surrender from Earth.
  • Earth’s surrender should happen as quickly as possible to avoid public opinion souring at home.

Useful Information

This may be updated as more information is requested.

  • Wormhole-based FTL travel exists (hand waived) that allows medium-large ships to travel long distances quickly, but is expensive.
  • Earth is ruled by a single governing coalition.
  • $\begingroup$ Not an answer because politics isnt my forte. After reading your bonus objectives I concluded that the earth can't threaten mutually assured destruction, so the only thing I can think is: *Ask for a peaceful surrender, to avoid waste of life and resource on a war thats basically lost *Drop a nuke/asteroid. *Threaten total annihilation if they dont surrender immediately *Keep dropping nukes/asteroid in a controlled manner, while secretly offering GREAT deals to the earth coalition's leaders. Eventually the fear of the nukes plus the deal will get the leaders. $\endgroup$
    – Silver
    Dec 16, 2015 at 21:24
  • $\begingroup$ Blow it up... like Alderaan. $\endgroup$
    – Kit
    Dec 17, 2015 at 0:35
  • $\begingroup$ Earth is ruled by a single governing coalition. - Great. Nuke them $\endgroup$
    – Richard
    Dec 23, 2015 at 20:41

9 Answers 9


There are two main ways to do this that I can see, in addition to what has been suggested already.

  1. You turn things back to the dark ages by destroying modern shipping and infrastructure...or
  2. You take away the sun.

Option #1

As things now stand, any fleet that controls orbit can deny the planet the ability to reach orbit, because a rocket trying to escape gravity has no ability to dodge a missile or laser from space.

The orbital fleet could also put a stop to all long range or slow moving vehicles...planes, trains, and most ships would be a thing of the past.

This would set the planet's economy back many centuries. If something isn't local, it can no longer be obtained, except by the extremely rich.

The destruction of satellites would mean long range communications are crippled, especially if the endpoints of communication cables under the oceans are destroyed as well. This might be enough to fracture the world government into feuding regional ones, especially for areas that can't feed their people without food imports. Those areas will be desperate to surrender once they begin to starve.

But the space fleet could also target power plants, power transmission facilities, bridges, important factories, desalination plants, oil pipelines and refineries, mines, irrigation and water supply pipelines, communications and sewer infrastructure, all kinds of things.

With orbital bombing, you could reduce a planet to the dark ages with tiny to medium civilian casualties, depending on how ruthless you wanted to be. Remember, a power plant has civilians in it, but you can just target the power transmission lines and facilities, and black out cities without killing a soul (but far more effort for the fleet).

Similar rules apply for water, communications, and other resources. It's too easy to hit things from space, and too hard to shoot back at the enemy, especially if Earth's military can't get any power or metal for the ground-based laser that they keep blowing up before it's finished anyway.

Option #2

To be even more oppressive yet impressive the fleet could deploy huge reflective sheets in an orbit identical to Earth's but close to the sun, so they cast huger shadows farther back from the light source. If Earth doesn't surrender...You block out the sun with these reflective sheets.

No light, no heat, no plants, everything dies without a bullet being fired. Once Earth surrenders, probably within weeks, you simply rotate the sheets 90 degrees so they don't block any perceptible amount of light and things soon return to normal.

  • 1
    $\begingroup$ Very well written and comprehensive answer, but terrible formatting. The good 'ol wall of text that no one wants to read. $\endgroup$
    – AndreiROM
    Dec 17, 2015 at 5:59
  • 2
    $\begingroup$ Thanks for the feedback. Sometimes it's hard to know what to leave out while still fully explaining things, or what to include so people don't bring up problems with your answer you could have addressed in the first place. Fortunately, my wall of text solves both problems by stopping anyone from reading unless they're interested. ;) $\endgroup$ Dec 17, 2015 at 7:24
  • $\begingroup$ Great answer. Hitting core strategic points to drive down technological capabilities is a very interesting option. Removal of light is also a nice way to prove world-ending superiority without immediately killing large numbers of people. $\endgroup$
    – Avernium
    Dec 17, 2015 at 15:16
  • $\begingroup$ "in an orbit identical to Earth's but close to the sun," that's a conflicting statement $\endgroup$
    – Trish
    Nov 10, 2020 at 16:59
  • $\begingroup$ @Trish It seems the intention is to say "an orbit of identical period to Earth's, but closer to the sun". Normally, that would also be impossible, except perhaps if they used the Earth-sun L1 point. $\endgroup$
    – Qami
    Oct 4, 2021 at 17:54

Stuff a bunch of ships with small pieces of scrap, essentially giant pipe bombs, and detonate them in orbit. Assuming ground to space transport is similar to today's technology (chemical rockets) you've effectively blocked a spacecraft from safely achieving orbit, at very little cost.

This has hopefully triggered what is known as Kessler Syndrome (https://en.m.wikipedia.org/wiki/Kessler_syndrome) as depicted in the film Gravity. As a bonus you probably take out the majority of orbital satellites dealing a blow to earth's communication network (furthering your other goals).

If you're more interested in Earth surrendering, given the scenario of space dominance, you can simply set this scenario up without detonating the ships and hold Earth to ransom, merely threatening Earth to surrender or never be able to safely make it into orbit for generations.


Ask the modern Western armies how to do it. You can literally make a living answering this question as a high ranking officer in the military. This question is indistinguishable from the question of how to fight against an opponent who is using guerrilla warfare. The question provides no information about the military of Earth, other than "Earth is ruled by a single governing coalition," so the question you are asking is on par with asking how to defeat Al Quaeda, but not the small middle eastern version from real life, but a global force focused on breaking the blockade.

The answer will not be a quick battle, as New Earth wants. The war will be long, protracted, and centered on observing what Earth is doing, and reacting to it. Eventually (maybe after 50 or 100 years), you may be able to separate the military (targtes) from the civilizans (innocents) and issue a final strike.

  • $\begingroup$ 50 or 100 years is probably optimistic in the extreme. $\endgroup$
    – AndreiROM
    Dec 16, 2015 at 22:42
  • $\begingroup$ @AndreiROM I accept that criticism =) We know absolutely nothing about the culture/military of New Earth and almost nothing about the culture/military of Earth, so maybe they just get lucky and New Earth-ians find a weakness quickly and exploit it $\endgroup$
    – Cort Ammon
    Dec 16, 2015 at 22:46
  • $\begingroup$ it wasn't criticism so much as I was agreeing/underlying your point. If he wants to maintain control over the long run the OP is screwed. $\endgroup$
    – AndreiROM
    Dec 16, 2015 at 22:48

Take a look at the novel Fallen Dragon by Peter F. Hamilton. In it the author describes a future in which wealthy, developed worlds loan colonists the start-up funds needed to set up shop on a new planet. A century or two later those colonies have to pay up the loan - plus interest, naturally.

A couple of generations removed from the initial colonists, however, the local population rarely feel like they owe those worlds/companies money anymore - especially as the amount is typically crippling.

So those companies/worlds have several "debt collection" fleets on standby. These fleets are equipped with state of the art weaponry (typically far superior to anything the colonists have, although as the novel progresses these lines begin to blur, and the occupying troops have more and more trouble maintaining control).

They rely on taking control of the planet's government and key services in the first wave, such that the locals are then dependent on them.

Of course these troops sort of have the law on their side, and they're not there for the long run, just to loot the world.

Quite frankly, and invading army should be prepared to execute rebels publicly, and to yank the leash quite hard on any dissenters, or protesters. If killing them is off the table then long-term internment camps should probably come into play, which won't be a popular move, but will get a message across.

By seizing control of key industries and services (such as medical supplies, food distributions, etc) the occupying force can buy the obedience of the masses by prioritizing people who obey, etc.

At the end of the day it won't be easy, and it will be bloody.


After defeating Earth's space fleet you send your fleet into orbit about Earth and demand their surrender.

If that's not adequate to get what you want you keep throwing rocks (small ones, not planet killers) at food and power production facilities until they do capitulate. If your aim is genocidal you simply engage in such bombardment anyway.


Develop a devastating virus (zombie virus?). It will annihilate all humans because it is a virus (rarely, if ever, mutates to other species). Have it to have a long "dormant" period, so that it infects all people and THEN symptoms start to show and people die off. Once all hosts are dead, the planet is as good as new.

Sounds easier and cheaper than all the asteroid stuff above.


Surround the planet with rapidly orbiting antimatter mines.

Earth will have significant trouble launching a ship or a missile through a dense field of antimatter mines. Wrap the antimatter in a fragile container to keep it from interacting with random particles. The interior of the container is a vacuum, so any mines that accidentally deorbit will annihilate in the upper atmosphere when they collapse.


This is how i would conduct the assualt:

  1. Psychological warfare by hacking most major buisnesses and crashing financial markets, not only this, but sending propaganda messages throughout the internet by bribing local humans with rewards to post them. You could also use the internet to study your enemy population's weaknesses.

  2. Destroying all artificial satellites and space stations in orbit, this would not only add to the earth's debris field making it harder for the enemy to send forces up to attack you, it would cut most communications i.e. gps, sat tv, sat phone, sat radio, and it would also cripple all of the orbital military assets.

  3. Then, detonate a large scale emp over most populated areas frying a vast majority of the electronics, which would shut down most transportation, communications, and cripple major industries and hamper the defenders.

  4. fire kinetic weapons at all major military facilities to render them useless in order to further discourage resisitance. You can also target power generation facilities, Spaceports, harbors, airports,major road hubs, and even if you wish centers of political power i.e. whitehouse, capitol, buckingham palace etc.

  5. then since you live on new earth drop a swarm of genetically modified locust-like bugs with an immunity to most pesticides, onto major agricultural areas to eat the crops and cause them to start starving.

  6. Then you demoralize the defender further by starting to target monuments, and areas of cultural significance with kinetic weaponry.

  7. Drop the gay bomb, a weapon that fills an entire area with female sexual pheromenones and it would make the enemies sexually attracted to one another, hetero, and homosexually, this would drive the productivity of enemies lower, and make them have an increase in venereal disease, and STDs. Drop these over most populated areas.

Note: steps 7 and 8 will only be used as a last resort if there continues to be centralized resistance. If there is no organized resistance skip to step 9.

  1. set forests alight using thermobaric and napalm based weaponry, use microwave rays to cause vibrations and create earthquakes, drop small asteroids/kinetic weapons to create miniscule tsunamis, and drop non lethal chemical weaponry (highly potent teargas, knockout gas) over wide areas to provide an increased psychological effect.

  2. destroy the moon. This will disrupt the ecosystems on the planet extremely badly.

  3. Then you start landing colonization forces to create settlements and act as saviors with advanced technologies to save the populace from it's primitive existence and slowly take them over from the inside by turning them into serfs who depend on your tech to sustain their lifestyle.

If the governemt of the world surrenders at any stage you will accept their surrender and land to discuss terms and start a peaceful occupation, and provide aid to the survivors.


Good (effective) answers to this question rarely make good narrative. If Skynet had just poisoned us on day one we wouldn't have ever gotten a movie franchise.

Loss of life and planetary destruction avoidance are noble goals... but nothing short of the promise of annihilation is going to get the job done.

Ideally, they will surrender completely before anyone dies, but the problem is pulling your punches might make them believe they have a chance, one action big enough to kill everyone in one shot with just enough lead time for them to verify, but not act on.

You say wormhole technology exists? Drop a wormhole generator into low altitude orbit with the intent to vent all their atmosphere to the next star system. Give them 5 minutes.


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