If you want to be a total ass, their motto can be "People should know when they are conquered."
Fuck me, yeah, if you want, your military's mottos could totally be based on wise and historic sayings from ancient mysterious and obscure Earth mythology like...
"If it bleeds we can kill it."
"Remember when I said I'd kill you last? I lied."
"Come with me if you want to live."
“To crush your enemies, see them driven before you, and to hear the lamentation of their women!”
"You know what killed the dinosaurs? THE ICE AGE!"
This so kicks the shit out of using mottos from every other special forces group today.
