like lambs to the slaughter

Without concern for what is to come (because one does not foresee the trouble ahead). This phrase comes from the Bible. When I did business with Michael, I was like a lamb to the slaughter—I had no idea he was such a criminal mastermind. The poor kid and his defense team weren't aware of what the prosecution had in store—it was like lambs to slaughter the moment the trial began.

Fig. quietly and without seeming to realize the likely difficulties or dangers of a situation. Young men fighting in World War I simply went like lambs to the slaughter. Our team went on the football field like lambs to the slaughter to meet the league-leaders.

Helpless and unaware of danger. This figure of speech first appeared in the Old Testament’s Book of Isaiah (“He is brought as a lamb to the slaughter,” 53:7) and again in the Book of Jeremiah (“I was like a lamb or an ox that is brought to the slaughter,” 11:19) and has been repeated ever since. In recent decades it was sometimes changed to like pigs to the slaughter, with essentially the same meaning.