Phrase(s): like a lamb to the slaughter
Go to like lambs to the slaughter.
McGrawhill's American Idioms And Phrasal Verbs
Also, as lambs to the slaughter. Innocently and helplessly, without realizing the danger. For example, She agreed to appeal to the board, little knowing she would go like a lamb to the slaughter. This expression appears in several biblical books (Isaiah, Jeremiah), and the simile itself was used by Chaucer.
American Heritage Idioms