re: do you think it's possible to win a war without putting boots on the ground

What kind of war and what objective? Your question is too general to be answerable. Here an example: If PROC attacked ROC and ROC (with a little help) sunk so many ships that PROC changed it's mind about invading, I would call that a win even though ROC put no "boots on the ground." GB held off Germany across the channel without putting boots on the ground of mainland Europe. That was pretty much a win even before D-Day. The US obtained a surrender of Japan without invading the Japanese mainland.

So while somthing like those examples would likely make up only a small minority of wars (or parts of wars), I think that, depending on the objective, like simply preventing an invasion, can be done without doing so.