Aren’t there certain condition? Even when we conquered EY, didn’t we have to give the goyim the option of keeping 7 Mitzvos bnei Noach and living peacfully with us?
I don’t think that we are allowed to just go decide to make war with another country.
Also, that is kind of like saying that it was okay for the Nazis to kill the Jews because we have a Mitzvah to kill Amelek.