semper fidelis
Always faithful — a pledge of loyalty that does not expire.
“The regiment's motto is semper fidelis.”
“He signed every letter to his old unit the same way — Semper Fi.”
“The eulogy made much of semper fidelis, and everyone present understood that the loyalty being described had been owed less to the institution than to the eleven people who had served beside him.”
Loyalty was a sworn matter in the Roman army. A soldier took the sacramentum, an oath binding him to his commander and his standard, and fides — good faith, the keeping of one's word — was a virtue with its own temple on the Capitol. Semper fidelis, always faithful, is built entirely from that vocabulary, though as a motto it is later than Rome.
Cities and regiments picked it up across medieval and early-modern Europe: Exeter, Lviv, St Malo and a long list of military units all carry it. The United States Marine Corps adopted it in 1883, and it is that use — usually shortened to Semper Fi — that most English speakers meet first.
The phrase is used seriously, as a motto, and warmly, as a sign-off between people who have been through something together.
Hannibal, Pyrrhus, and the strategy Rome used on everyone else.
- 01
Hannibal at the gates (idiom)
A threat so close and so serious that everything else stops mattering.
Hannibal in Italy, 218–203 BC.
- 02
a Pyrrhic victory (idiom)
A win that costs so much it feels almost like a defeat.
Pyrrhus beats Rome and loses anyway.
- 03
divide and conquer (idiom)
To keep opponents from uniting so that each can be dealt with separately.
How Rome handled the defeated.
- 04
fortune favours the bold (idiom)
Luck tends to go to the person willing to take the risk.
Virgil, Aeneid X.
- 05
si vis pacem, para bellum (idiom)
If you want peace, prepare for war — the argument that strength is what prevents attack.
Vegetius on why armies train.
- 06
casus belli (idiom)
The event a side points to as its justification for going to war.
The paperwork of a just war.
Last updated August 3, 2026