This is an ancient Roman saying. As a ruler, we prepare for
what we want; we do not wish for its opposite. Here the contradiction is
verbal, not material.
The meaning of the saying is to be strong and of that
enemies will beware of warring with you. It is not war of aggression for which
you are to prepare; in aggression war preparation is meant to end in war, but
war to defend rights.You stand on defense. There are many instances in history of a strong army or navy ensuring peace and of a weak army or navy inviting the inscription: “Happy is the city which in time of peace thinks of war”. At the same time it should be borne in mind that the pulling up of huge armaments even when honestly intended to secure peace, might cause war.
For,
“How oft the right of means to do ill deeds”.
Make deeds ill done!