How to judge the Mark 27 homing torpedo

How effective was the Mark 27 homing torpedo in World War II?

It was a useful first-generation weapon: far from modern performance, but better than having no homing option at all.

The Mark 27 offered a commander a capability that earlier weapons had not provided. Its value has to be judged against those available alternatives and the limits of first-generation equipment. It receives a positive assessment for its own period, without any claim that its performance would be satisfactory today. The useful comparison is the extra tactical option it created during World War II.