Ense petit placidam sub libertate quietem

Ense petit placidam sub libertate quietem is a Latin phrase meaning "By the sword we seek peace, but peace only under liberty". It is the motto of both Massachusetts and the University of Massachusetts Amherst.
It was written around 1660 by Algernon Sidney, a member of the British "long parliament". He was an opponent of Charles II, who had him executed for treason.