1. The Klingons were teaching the natives how to make them. 2. You going to keep a ship in constant orbit to monitor them? Because nothing stops them from bringing more once you leave.
That some people don't like it doesn't mean it didn't work. The TNG-first crowd needs to get over itself. --Sran
Good point. Relatedly, this is not the same situation shown in "Too Short a Season," which was a clear weapons-for-hostages situation. I guess, then, the Kirk version would have more of a bent that of cowboy diplomacy backfiring... which actually would not paint Kirk in that bad a light, IMO.