Hand operated winch could be the go.. (same principle as the lever block I guess?) We've pulled the rally car out of a few ditches with one of these, so I'm sure it could move the caravan if the ground is level enough.
Not really any way to anchor it to the ground I don't think, but if there's a tree or two handy then consider it anchored
If you really want to make it easy, get some air into both of those tyres first.