An Analog or Asimov's sci-fi mag publication, I think. The leader of war that was fought and won in the far future has chosen to settle on an idyllic out-of-the-way present-day planet. He's making friends, perhaps finding love, but he has the rotten luck of rogue soldiers under his former (future?) command who also pick this particular spot in the continuum for their peace-time retreat. They bully his friends and threaten much worse with supernatural future-soldier powers. Our hero faces a hard choice: abandon this relatively insignificant place to the bad guys and ensure the future peace of the universe, or reveal himself and his own powers and be forced to destroy the rogue soldiers and return to the future and fight the war again. Of course he squishes the bad guys and bids sad farewell to his friends.