Right at the beggining of the invasion

This Pokémon world had been populated by nothing but Pokémon for centuries, as far as their recorded story can trace back and humans are only talked about in fables, so when some strange people ships began to land on their cities and out of it came the humans whom they usually thought were just old legends the reactions were varied, some were just frozen in shock, some were panicking while others were just surprised but casually optimistic that the humans could be friendly, but those last ones turned out to be the more wrong as the humans were soon attacking them and trapping them against their will in small spherical prisons they called pokeballs.

Soon enough, fear and anger were felt by the Pokémon being abused and enslaved by humans who weren't sure how to fight back. They were physically weak compared to even normal Pokémon, but they had such overpowered technology that they could even force legendaries to submit.