too much latin to choose from.
deus vult - God wills it
deus nobiscum, quis contra? - if god is with us, who is against us?
de mortuis nil nisi bonum - (say) nothing but good about the dead
dulce bellum inexpertis - war is sweet to those who have not been there
dulce et decorum est pro patria mori - it is sweet and glorious to die for one's country
iacta alea est - the die is cast
Any of those could be chopped a bit. better stop before this post is moved to the classicists' forum