basic strategy for white - the "draw fort"
Look at this situation. White is really hemmed in, and black has succeeded in blocking all the corners. Has white lost this game? No! In this position, the white king can move back and forth forever, and there is nothing black can do about it. The situation is a draw. Better than a defeat! Positions like this are called "draw forts" - the white warriors have formed a defensive "fort" around their king, protecting him and also reserving a spare square, so he can move back and forth.
There are many different draw forts, some at the edge of the board, and some in the middle.
Black must try to stop white from achieving a position like this, in order to avoid a draw, after all, black still hopes for a win.