From the classic Latin “Si vis pacem para bellum” [0]
I’d always interpreted this to imply that deterrence was good - appear strong to prevent others picking a fight with you, rather than studying.
I always wondered if the 9mm Parabellum cartridge was named after the saying too, but no such enlightenment is available on the Wikipedia page at least [1]
While it's true even today,I think at the time it was heavily related to the fact that most countries usually had to raise money and hire majority of soldiers when facing/declaring war rather then keeping them on payroll permanently. So if an enemy is banging at the gate, it's a bit too late to start sending message around 'we are hiring'.
https://de.wikipedia.org/wiki/Parabellumpistole