Need correct call to Promise reduce (when.reduce )

I have a processor function that takes a "cmd" object and returns a promise where the resolution is the same "cmd" object passed in (with a response key added). reduce here is when.reduce

 reduce = require('when').reduce;

  //return processor(cmds[0])
 return reduce(cmds, function(processor, cmd) {
     Debug.L1('running processor for component ', cmd.component)
     return processor(cmd)
   })
   .then(cmds => {
     Debug.L1('cmds with responses\n', cmds)
     let response = cmds.map(cmd => {
       return cmd.response
     })
     console.log('the complete response is\n', response)
   });

This does nothing, it does get to the .then but the array of promises never fires, never see the Debug running processor...

If I run just a single processor it works great cmd[0], cmds[1], etc.

return processor(cmds[0])
//return reduce(cmds, function(processor,cmd) {
//       Debug.L1('running processor for component ', cmd.component)
//   return processor(cmd) })

What am I missing here? Their api and wiki examples aren't giving me any insight.

IMPORTANT UPDATE: The answer below does work but throws unhandled rejection errors. The culprit is the when library. It seems no longer active and has not been updated since node 6. I switched to bluebird and it works fine without any change to the code outlined below.

I'm still not sure what you are looking for, but it might be

reduce(cmds, function(responses, cmd) {
    return processor(cmd).then(function(response) {
        responses.push(response); // or whatever
        return responses;
    });
}, []).then(function(responses) {
    …
});

Before trying to understand when.reduce, you might want to have a look at the non-promise array reduce.