It is easy to be brave from a safe distance.

Aesop (620?-560? BC) Legendary Greek storyteller

Fables [Aesopica], “The Wolf and the Kid” (6th C BC) [tr. Jacobs (1894)]
    (Source)

Alternate translation: "Time and place often give the advantage to the weak over the strong." [tr. Townsend (1887), "The Kid and the Wolf"]