D'fior chogaidh comhailtear síothcháin.

D'fior chogaidh comhailtear síothcháin.

(to / for * man * of-war * is kept / maintained / observed * peace)

By a man of war is peace maintained.

This is the first line of the first quatrain in a poem that Tadhg Dall Ó Huiginn addressed to Brian na Múrtha Ó Ruairc (c. 1540 – 1591):

D'fior chogaidh comhailtear síothcháin,
seanfocal nách sároighthear;
ní faghann síoth acht fear faghla
feadh Banbha na mbánfoithreadh.

Roughly:

By a man of war is peace maintained,
this is a saying that cannot be refuted;
only the man of attack finds peace
throughout Ireland of the grassy slopes.

See "Na sluaig na saiget segair" in this collection for similar advice. Or look back to the Romans: Si vis pacem, para bellum.