Could we actually fight a war against an alien race?

[Cirio]

snakenobi said:

aliens don't exist and never will

we are the only ones in the universe

even if aliens existed,they would have a different dimension

they should have developed around the same time as earth did from the beginning of the universe and have the same kind of materials as us to even realize that they are there

Define "alien". What if there are plants or bacteria that exist in another planet? Those would be considered alien.

OT: No because I doubt there is another life form out there that is intelligent like us.