Si vis pacem, para bellum is a Latin adage translated as, "If you wish for peace, prepare for war".
How To Say "If You Want Peace, Prepare For War" In Latin?
Si Vis Pacem, Para Bellum. (Guaranteed).
The usual Latin saying is "Si vis pacem, para bellum." There is a full explanation of this here. The saying itself is based on a slightly longer saying by a Roman military expert.
If You Want Peace, Prepare For War