Whats Christan beliefs or bible say about joining the army?

im hoping to join the army when i get old enough but i know that if you kill you go to hell im wondering if there is something about that because in the army you shot them and kill people sometimes but i wonder if that counts i hope for a professional to answer that question or whatever (i know this sound kind of werid for christain belief maybe. please dont judge me about how i said this)