So, as you go into battle, remember your ancestors and remember your descendants.

[Et majores vestros et posteros cogitate]

Tacitus (c.56-c.120) Roman historian, orator, politician [Publius or Gaius Cornelius Tacitus]

Agricola, ch. 32 [tr. Acheson, ch. 4, para. 22 (1938)]
    (Source)

Alt. trans: "Think of your ancestors and your posterity" or "Think of your forefathers and posterity."