Alien species be it from the enemy, neutral, or from the Gods have been visiting Earth all the time, the Gods know everything, there is no need to worry about anything, it's not an important factor.
To add here, I don't think brute force for them is practical. The distances between the planets are vast for one. Along with this, each saucer would have to be capable of transporting a certain number, then weapons and do forth. The number of the enemy would have to be enough to physically conquer the number of humanity.
Greys for example, from what I've learned, must have special breathing apparatus and such to physically survive in our environment. I read where they carry breathing packs on their backs. I don't write "oxygen" because they more than likely don't breathe oxygen the same as we do. They also breathe and secrete through their skin.
So... There appears to be strong reasons why worlds are conquered through the means of psychic power.
To add here, I don't think brute force for them is practical. The distances between the planets are vast for one. Along with this, each saucer would have to be capable of transporting a certain number, then weapons and do forth. The number of the enemy would have to be enough to physically conquer the number of humanity.
Greys for example, from what I've learned, must have special breathing apparatus and such to physically survive in our environment. I read where they carry breathing packs on their backs. I don't write "oxygen" because they more than likely don't breathe oxygen the same as we do. They also breathe and secrete through their skin.
So... There appears to be strong reasons why worlds are conquered through the means of psychic power.