# si vis pacem, para bellum

idiom · CEFR C2 · Formal

Source: https://englishreference.com/idiom/si-vis-pacem-para-bellum
Updated: 2026-08-03

## Meaning

If you want peace, prepare for war — the argument that strength is what prevents attack.

## Examples

- The defence minister quoted the old rule: si vis pacem, para bellum.
- Successive governments justified the budget with si vis pacem, para bellum, and successive oppositions asked what exactly was being prevented.
- Si vis pacem, para bellum has the great advantage of being unfalsifiable: if war comes, the preparation was inadequate, and if it does not, the preparation is why.

## Origin

The source is Vegetius, writing his handbook on military affairs around AD 390, at a point when the western empire's armies were visibly failing. His sentence runs: therefore he who desires peace, let him prepare for war. He was not being philosophical. He was arguing for training standards, and his point was that an army nobody fears will be tested. The compressed form si vis pacem, para bellum is the version that travelled, and it became the standard justification for peacetime armament in European politics — quoted by people who found in a late-Roman drill manual exactly the sentence they needed. It also survives in an unexpected place. When Georg Luger's company developed a new pistol cartridge in 1902, they named it after the second half of the motto: 9mm Parabellum.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.