- Radar is a method of locating invisible objects, [and was] used first in World War II for the detection of the approach of enemy aircraft and submarines, and later [Radar was] put to peacetimes uses.
The last two ('was used' and 'was put') are in passive voice, making 'used' and 'put' past participles, not really verbs.
The phrase 'peacetimes uses' sounds awkward to me. It's a new one for me. I want to edit it to 'put to use in times of peace.'
Student or Learner