In the months following the submergence of R’lyeh, there was silence from the sea. Humanity began to slowly rebuild and reclaim the severely damaged Earth. The planet is now covered in perpetual clouds and the brightest days are no more than a dim twilight. The unusually dense nature of the clouds, and the unnatural colors and frequency of the lightning that flashes within them, indicate more than natural forces are at work.
For a time the denizens of Cthulhu watched patiently from their protected cities. They eliminated any threats that came close and were particularly baffled by the unarmed vessels that would occasionally approached and utter a human word over and over, “peace”. It was an alien concept to them and it took their human cultists a great amount of time to make them understand the meaning. Once they did, they simply laughed and fed the crews of these vessels to their minions.
Eventually the enemy began their attacks again, although this time at a much slower pace. First, simply protecting their ocean cities and then spreading out to the sea once again and finally the land.
During the brief respite, humanity did not sit idle. There was a change of tactics and for the first time in recorded history, humanity joined as one. They created a united front against the enemy. As part of the H.A.D.E.S. (Human Alliance in Defense of Earth and Sea) Treaty, all the remaining militaries were combined into a unified Earth military under the jurisdiction of the Aligned Nations of Earth.
The human population is now split between the Earth and the moon. Those on Earth reside within heavily fortified cities far inland. Inhabitants of the moon live in crowded colonies inside ancient lunar lava tubes with just enough food and water to survive. Each population center is reliant on the other. Earth provides food and most of the water for the colonists on the moon and the lunar colonies act as a staging point and produce Helium 3. This gas is needed for power generators and weapon systems as most of the natural fuel sources on Earth are now out of reach or too dangerous to collect.
With all the scientists of Earth working collectively, breakthroughs in weapons and defensive technologies has increased a hundred fold. New technologies or reverse engineered enemy technologies are constantly being discovered and deployed to the battlefield. The human armies are a mix of regular human infantry, GECS (Genetically Engineered Cybernetic Soldiers), semi-autonomous robots and mobile weapon platforms. There are also rumors of a top secret project between the H.A.D.E.S. scientific branch and The Order which is said could significantly alter the direction of the war. Little else is known except for a whispered code name, Project Helios.
For now, Earth remains a battlefield and the glorious future among the stars that humanity dreamed of for so long has been denied. In its ever growing desire to expand beyond our planet, mankind failed to see the threat that would shackle it to the ground.