Ab urbe condita

Titus Livius (Livy)

Livy. History of Rome, Volumes 1-2. Roberts, Canon, Rev, translator. London, New York: J. M. Dent and Sons; E. P. Dutton and Co., 1912.

Thinking that the ferocity of his subjects might be mitigated by the disuse of arms, he built the temple of Janus at the foot of the Aventine as an index of peace and war, to signify when it was open that the State was under arms, and when it was shut that all the surrounding nations were at peace.

Twice since Numa's reign has it been shut, once after the first Punic war in the consulship of T. Manlius, the second time, which heaven has allowed our generation to witness, after the battle of Actium, when peace on land and sea was secured by the emperor Caesar Augustus.