Earth appeared peaceful from orbit. It was full of vibrant color and beauty uncommon to the rest of the system it called home. It also had the distinction of being able to support life, fortunate enough to be in the perfect Goldilocks Zone. The Vortaak General Ardal looked out the window of his command ship with a sly smile gracing his grey-skinned face. He wore a gray soldiers uniform adorned with black body armor, the armor a trait among Vortaak leaders. He thought to himself, that the time had come. His forces had observed the planet for numerous Earth decades, and he felt the time was right. They possessed enough data, and their forces were specialized enough to handle the environment of this new world. He was certain he would return home to his queen with a new home for his dying world.
His planet had been suffering severe droughts and famine from a civil war that seemed to never end. The great Vortaak empire had been slowly turning its home into a desolate, rocky wasteland. He worried that one more nuclear detonation would shake the planet's core into oblivion. An exaggeration, of course, but he knew there was little time. Transmissions from Vortaaka were becoming more and more desperate. He had to act now.
In a language incomprehensible to humans, he ordered his men to send out the fighters and release the first wave of monsters. He watched as a series of saucer-like ships left the disc-shaped mothership. General Ardal found it humorous how his scout ships had become common among human conspiracy theories, serving to divide them further. He saw signs of his own people in their culture. Always so divided on the most trivial of things, sometimes resorting to war over simple trade disputes. They were a young race that fortunately had yet to make all the mistakes the Vortaak had. He knew the seeds were planted though. The stockpiling of weapons, political corruption, mass pollution, the holes of their graveyard were neatly dug. General Ardal almost considered their annihilation a swift act of mercy before they were to face the guilt of their self-destruction.
The Vortaak invasion force was primarily concentrated in the Pacific Ocean. It was Earth's largest ocean and any major resistance would have to be sent by their slow moving sea ships or their primitive aircraft. The perfect setup until they could expand into the continents. They attacked the west coast of the United States, primarily Seattle and Los Angeles, while the other forces attacked Osaka and Tokyo in Japan. The goal was to slowly gain ground across the planet and then call reinforcements to cleanse the planet completely.
General Ardal was confident. However, he realized Earth had a natural defense in the form of giant monsters, similar to their own. His goal was to capture them and bring them under his control or kill them. It made no difference to him. He had observed them over many years and was confident he understood their strengths and weaknesses.
First, there was Godzilla. He was considered the king of the monsters by the humans, and General Ardal was willing to agree. He certainly appeared to be the mightiest. Godzilla first appeared in the Earth year 1954 as a byproduct of American nuclear testing and was once the sole survivor of a species of aquatic reptiles. He went on to rampage in Tokyo leaving it in ashes. A chemical compound known as the Oxygen Destroyer was used that nearly killed the creature and drove it away. Unfortunately for humanity, the monster would return numerous times in the coming years.
Anguirus was a loyal companion to Godzilla but they first started off as enemies back in 1955. They had a near-death duel in Osaka after fighting their way savagely through the Pacific from Iwato Island. The humans and even the General himself were unsure of the creature's origins, though the low level of radiation emitted from the creature suggested he is another radioactive mutant like Godzilla from prehistoric times. Anguirus never appeared to bother humanity again, but General Ardal knew the monster was alive and well.
Rodan was a lonely creature that did not associate with the other monsters much. He was first discovered in 1956 after being released from a mountain by a Japanese mining operation. Eventually, he made his way to Fukuoka on a feeding frenzy. After many losses, the JSDF lured the pterosaur back to Mount Aso and buried within. It was effective until it broke free in 1964. The specifics of his origin are unclear as well but he may have been a surviving pterosaur mutated by atomic testing.
Aside from Godzilla though, there was another monster that concerned the General. An ancient protector of Earth that is worshipped as the Goddess of Peace by the natives of Infant Island. Mothra. Although appearing as an ordinary moth-like creature, she is far from one. She has been known to have almost magical abilities, so many that even General Ardal could not comprehend. She only began to interfere in modern human affairs in 1961 when Infant Island was discovered. Two of her priestesses were kidnapped by gangsters and held for ransom in Tokyo to exploit Japan's monster fear. The thugs hoped to receive a large sum of money from the Japanese government due to the impending attack by Mothra. Mothra arrived, very angry, and rampaged through Tokyo. Since their plan had failed, the gangsters fled the nation to return to New York City. Mothra followed them there and rescued her priestesses successfully, resulting in massive damage to the city as well as the deaths of the thugs. After that, she left peacefully after giving humanity a reminder to not disrespect their guardian. Relations with Infant Island improved after diplomatic talks but the villagers preferred to remain isolated. Mothra would return to civilization numerous times but as a protector, not an invader. Human and Vortaak science has failed to explain her powers, leaving many to believe she very well may be a true Goddess.
After assessing the monster's data once more, the General settled into his command chair aboard the mothership. He awaited the fall of Earth, confident in his armada.