THE RIGHT WAY: SURPRISE!
Obviously, I would have done things a little differently.
The opening moves of an invasion should come as a complete and total surprise. This is true of any offensive, anywhere, at any time. If the opponent knows when and where you’re going to strike, you can expect a serious counterattack. At best, you’ll be wasting firepower on empty positions. You want troops and population caught without warning. You want defenses down. You want vital targets to be relaxed so they are easy to capture or eliminate.
The first time the Earthlings see your ships should be a split second before your offensive hits. It’s even better if your target never knows what hit them.
To do this you need two things: a detailed plan of attack with a firm schedule of operations, and a method of approaching your objectives while remaining undetected.
The first part is entirely up to you. Plan, and plan well. You don’t just show up. That’s not an invasion, that’s tourism. You need a staging area where your forces can make final preparations. Now both the Gorgonians and the Sondrak Imperials did this. But what did you do wrong? You set up shop right in the middle of Mars, a planet that is under constant observation by Earth astronomers. The Gorgonians were spotted by a bunch of guys looking through telescopes with primitive glass lenses. The Sondrak were also spotted by astronomers. Again, these guys weren’t looking for alien aggressors; they were looking for comets and distant planets. How is it they managed to spot you?
Back then, the approaches to Earth were completely unguarded. You could have set up behind the other planets in the solar system, behind asteroids, even behind the planet’s own moon, and it’s unlikely that they would have detected you.
The Gorgonians didn’t have to deal with Earth scanners but the Sondraks were picked up by RADAR during their little adventure. That’s just lazy. As I pointed out, that system is easy to fool.
Before we get any further we should review sensors and long range detection. They come in two basic forms, Active and Passive. Active is like the human RADAR system. It sends out waves of energy that bounce off of objects the way a noise bounces off a canyon wall. That “echo” is then analyzed and depending on your equipment can tell information about the object in question; from its direction and distance down to its chemical composition. The drawback with Active sensors is that they are constantly “shouting” so they are easy to spot. Passive sensors on the other hand simply “listen”. They’re like ears that are always open. Some of them listen to sound, others “listen” to infrared radiation, magnetic fields, visible light, gravity, tachyon fluctuations. Two points to this. Number one is that you’ll never catch the Earth by surprise if you come in with your active sensors blaring away. The second is that Passive sensors are a lot harder to evade.
Here’s a little thought experiment. Suppose that the Sondraks had bothered to cloak their ships, they still had one major obstacle to detection left; atmospheric disturbance. Earthlings back then didn’t spend a lot of time looking up at their own sky, but they did notice some things like very large ships hitting the atmosphere at high speeds. Even though we have some advanced technology, we’re still talking about a lot of assault and landing craft displacing a lot of gas. It’s going to be visible. Even if you somehow lessen the effects of friction on the ship’s surface, there’s still no way to hide the atmospheric disturbance you’re causing. And a very large invasion fleet will cause a lot of disturbances. Which the Sondrak invasion fleet did. The Earthlings saw what looked like a massive meteor shower over California. It was just like holding up a sign that said: “We’re landing right here!” On top of that, the Sondrak ships emitted a magnetic pulse that played havoc with the electricity. Humans discovered their time pieces had stopped and their vehicles wouldn’t start. All of this, the light show in the sky, the electrical failures, were obvious to the civilian population. Can you imagine what it would look like to a passive sensor? The Sondrak should have taken better precautions. There are huge areas on the planet that contain very few humans – if any – namely the oceans and polar regions. The Sondraks could have made good use of these areas when they descended from orbit. Their ships should have been better shielded to avoid unintended EMPs.
Some have floated the idea that a mini warp or space bridge right on the planet’s surface is a fool proof option for achieving total surprise. Using the same principal that allows us to cross interstellar distances, you can make a small warp that transfers troops from a base on Earth’s moon directly to their surface.
The only problem with this is you have to build the space bridge on Earth. Sneaking a few ships onto the surface is a lot easier than concealing an entire invasion fleet. And the Earthlings lack the ability to detect a warp signature. But the real problem is: how many space bridges are you going to build, and where are you going to place them? You should place them close to your primary targets, but any such target will be defended. Plus, with all the nations and separate militaries on the Earth, it means there will be a lot of primary targets in the opening moves of the invasion. That vastly increases the number of space bridges you have to build very close to sensitive areas. That just increases the chances of the invasion being discovered.
Also, you make it very easy for the Earthlings to completely rout your attack. All they have to do is locate your space bridges and knock them out. Then your units are cut off.
No, space bridges are better saved for later stages in the campaign, once the opening beachheads have been secured and supply lines then become an issue. If you rely on them to deliver the unexpected blow, it might be you who’s in for the nasty surprise.
Now here’s the bad news. The Earthlings aren’t so easy to catch off guard, anymore. After all the failed invasions, they know anyone coming down there doesn’t have good intentions. They are on high alert and have a multinational organization responsible for sharing information related to possible alien incursions. And they have improved technology. They may not have mastered the use of tachyons and other advanced particles for detection and communication purposes, but they have learned a few tricks. And the deep space approaches are no longer unguarded. There are a number of deep space probes designed to look for Faster Than Light drive signatures. Small craft can dodge and avoid and arrive on the Earth undetected. But a large scale fleet? Out of the question. You want to sneak up on the Earth with an invasion fleet, you’re going to have to do some serious planning.