In my story, Earth gets invaded by evil aliens. Good aliens provide troops, tech, etc. to fight off the evil aliens, and the invasion is fought off in a month and a half. Here are some major events in the invasion, which starts in mid-November 2020 and ends on Christmas Eve of the same year:
- Sixty days before the invasion begins, a warning as cast across all devices, so TVs, radios, smartphones, etc. on Earth. It tells the people to prepare for war.
- When the invasion begins, before ground troops are sent, 195 antimatter missiles each packing the explosive energy of 1 Tsar Bomba are sent flying at each and every capital city on Earth. This causes the complete and utter breakdown of society, as well as starting a possible nuclear winter, but works to unify humanity as one.
- Four complexes are set up around the globe to limit interplanetary travel, and to provide base for troops. One is set up in northern BC's forests, another is set up on a remote Siberian island, another is set up in the Atacama Desert, and another one is set up in Challenger Deep. However, Earth's defenders are able to destroy each and every one of them halfway through the invasion.
- A counter-attack is launched, which succeeds in destroying the planet-sized flagship that is the alien invaders' main base of operations, and killing their godlike leader shortly afterwards, ending the invasion. The flagship has a bit more than twice Earth's radius and about seven times Earth's mass.
And here's the consequences afterwards:
- The presence of superhumans with powerful abilities is able to limit the aftershocks, but they're still there. Globally, about one billion people perish, making it the bloodiest war in human history by far.
- The environment is (obviously) in shambles, as there's now these big clouds of soot blotting out the Sun, and an planet-sized spaceship exploded.
- Whatever alien troops didn't switch sides, be KIA/MIA, or flee are kept as POWs.
- Earth becomes open to the cosmic community, with the people who saved it seen as war heroes. However, anti-alien sentiment runs high, but immigration and emigration to and from Earth begins.
- Reverse engineering of alien technology allows for a second Industrial Revolution, which aids the people of Earth with recovery.
- The massive empire of the alien leader, which has been existing ruled by one being for an uninterrupted million of Earth's years, and having territory that includes 1% of the entire universe, crumbles to a power vacuum. Warlords and crime lords, once united by respect and fear of the alien leader, now squabble over territory.
- Earth is forced into a global recession, but is now run by one democracy, led by the courageous teenage girl who was able to successfully unite Earth and allied beings and worlds under one banner, as its first-ever President. She serves for 8 full years before retiring, deciding that she's done enough helping people and deserves a break, and knowing that she has already created a gold standard that will result in her successors being derided for having the audacity to not be her.
And the flagship was located about six light-hours from Earth. The aliens have access to terraforming technology, which can be used to minimize, even reverse, the damage to the environment. The purpose of invading Earth was to use the superhuman beings that cropped up a bit more than a year there to build an army that could conquer the universe. I have tried calculating the consequences of the flagship being destroyed before, but it's only an estimate. Would the economic, environmental and human life toll be realistic?