[ WP ] Aliens come to Earth in hoping to wipe us out and take over the planet , but are honorable and gives us a fighting chance . They announce they will return in 100 years so as to give Earth a chance to prepare and defend itself . Neither side expected what the other would bring to war

Tick, tock. 
 
 Earths space fleet was ready. Well, the most ready they ever could be. 
 
 Decades of research had been poured in these top-of-the-line fighter craft. Ground-breaking achievements were made on every front. A never before seen united human spirit was born, and every country participated the best they could, the most they could. 
 
 In fact, countries were rarily named anymore. It was Earth. Not China, not the US, not Europe, but Earth. 
 
 Mankind had scrambled together 160 modern spaceships, 1405 satellite weapon systems, 2300 small spacecraft ( basically guided scraps of metal with penetrating explosives ) and a moon laser base. On the ground, hundreds of thousands of re-fitted space missiles pointed in every direction, connected to several computer networks to fire at one's command. Millions of camera drones were spread around for the inhabitants of Earth. 
 
 It obviously was not enough. 
 
 The last time they came, He had a fleet numbering in the tens of thousands. Earth managed to bring down two robot craft, and that was because of friendly fire on aliens behalf. 
 
 But the men would not go down without a fight. 
 
 He had the decency to come at the agreed place to fight, at the agreed time. A portal opened and thousands of black ships poured out. A large mothership lay in the middle of this monstrous battlegroup. 
 
 His voice boomed, and despite the vacuum of space, the space marine heard every word clearly. the alien leader captain Ea spoke to them. For the alien, this was purely for profit. Earth seemed to be valuable, he had said a hundred years ago, but he had not specified in what way. His army was entirely robotic. He controlled it and had defeated the defenseless Earth inhabitants. But he had the honour of a fair adversary. He had given mankind 100 years to'impress' him. 
 
 It was on. 
 
 The last time, mankind could not land a single blow to them. This was different... 
 
 Somewhat. 
 
 They traded unequally, losing five ships for one robot ship. But they could fight back. They were no longer the ants hundred years ago, but a small swarm of fiery raccoons fighting for their turf. 
 
 The human fleet slowly shattered, and the robot fleet reached Earth and started to face the satellites and the secondary reserve fleet, which was a ragtag of unfinished ships and defunct weapon systems. 
 
 Then, the command was given to launch the rockets. Future historians agreed their effective combat potential was negligible, but on that day, everyone could see space lit up with the soundless explosions, the growl of mankind. The battle raged on fiercely for hours. 
 
 It ended. Space debris floated everywhere, from both sides. 
 
 Ea's voice boomed again, this time in a different tone. `` Well... That was impressive indeed. You have honoured me with a challenge, and I deem your race worthy. `` 
 
 `` This galaxy is a dangerous one. A never before seen threat is spreading over the galaxy. In time, both of us will be affected by it. Perhaps in the future, we can be of assistance to one another. Until then, fare well.'' 
 
 The robot fleet then retreated through a portal and disappeared. In its wake were floating hulls, technology ripe for the taking for mankind. 
 
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 EDITED: advice taken from comments
