So what? Many characters shoot a gun better than the player, or know more about medicine than the player. I don't require them to give me detailed info about how they're treating a patient before I decide whether it's valid -- although I certainly wouldn't stop one. By this logic, you are giving characters an unearned advantage if their player is smarter than they are. Which is more defensible, since everyone wants to feel smart and cool. But it undermines the concept of roleplaying and, probably, other players at the table!
So, it's the same as any other skill in a roleplaying game. The player says what the character is trying to do, the GM evaluates whether they have the skill to do it, calls for a roll if necessary, and then puppetmasters reality accordingly. A great tactician can make a terrible blunder and a very bad one can get lucky once in a while.