Lets start with the presumption that there are cosmic laws in place which prevent advanced civilisations from conquering less advanced ones
directly.These laws would be enforced by godlike beings.
For example thou shall not directly kill a lesser being.
Thou shall not physicly damage a lesser being.
Thou cannot force a lesser being to act against his or her will.
And most importantly thou must use technology equivilant to the lessers civ in which to wage war with.
Given such directives lets say a civilisation a 1000 in advance to ours wished to conquer earth.But why you say?, well in 10000 years time earth will
be extremely powerful , a worthy foe for most.
Now lets also presume "those" a 1000 years in advance to us are capable of time travel, with this gift the most logical point in which to conquer
earth would be in its past, when they are weak and vunerable, naive and greedy.
Thus if time travel is a technology possesed by our invaders they will travel to a point in earths past, say the 1940's.why not earlier than the
1940's, well its hard to conquer a planet using guns and learjets isnt it ;-).
Now the second act they would wish to achieve would be to accelerate the speed of our technological progress so as to allow them to use funky death
rays and anti grav ships.the most logical place in which to accelerate such progress is in the worlds superpowers......
...Hence why we have black ops who seem to have tecbnology way beyond the norm.yet refuse to release it..it only has to exist somewhere on earth for
it to be counted as present tech.
The other way in which to accelerate technology is to leave gifts for us , we hear the astronaughts found a mobile phone esk device on the moon, we
hear that roswell contained sophisticated tech such as fibre optics,we hear the us of a was given many a shinny toy by our alien "friends".
I state such gifts, recovered ufos and such were nothing but a way of accelerating our technological state so as to allow "them" to use a similiar
level of tech against us.
The third directive in which they would wish to overcome not being allowed to harm a human directly.The way to get round this is to get humans to kill
other humans for them, this can be achieved by infilitrating organisations such as the military industrial complex and the cia and using them as pawns
in which to kill whomever they wished, eg jfk knows to much.you must kill him, mission accomplished.
Other ways are by sowing the seeds of war by getting nations to go to war with each other, by causing climate change by withholding alternate energy,
and most fearful of all tricking humans into using doomsday devices against a phantasmical foe of our future when infact the purpose is to eliminate
humans themselves whilst abiding with cosmic law.
The other directive to overcome is thou cannot force a human to act against his will.This is where we get into brainwashing, bribery and trickery.
We often her of brainwashing via mk ultra and such, its pretty evident its not humans behind most of it, it appears to be done by beings of higher
intellect , by systems such as remote manipulation of the brain by microwaves, wait a minute werent we gifted mobile phones in which a global net of
microwave emission and transmission has been established in order to accomplish this goal

.
We hear of mind reprogramming with electronic harrassment(research it) armies of manturian candidates to be used in project blue veam, syran syran,
all those crazy folk who go about killing people cos "god" told them to do it,(probably through the mobile phone network;-)).
We hear of powerfull government agencies being bribed with technology so they toe the line, we hear of people working for "them" for the good of
mankind, we hear of a cover up at all costs in order to protect national security, but whos security is this really?.
We see the MIB, who noone really knows whom they are, who turn up at scenes conviscate what they want and leave.Who are they cont....