Fortress in a pawn endgame

This position could have appeared in one of my old games, had I played 33. Bf2-e1!?

Black to move. Can he win by going into pawn endgame with 33…Nxc3?

I would be forced to take on c3, and we’d need to see if White has a good response here after 34. Bxc3 bxc3
White to move. How to create a fortress?

I blogged about another pawn endgame a couple of days ago, it was all pawn races and calculation. Here instead we need to think strategically – what plans does Black have, and how can we prevent them? Looking for the answer, you will see that Black’s protected passed pawn on c4 is going to keep White king tied up. Black king may then break through either on the kingside or on the queenside. We can keep queenside closed by playing a2-a4, but what about kingside?

35 . h6!! is the only way to create a fortress. 35… gxh6 (otherwise White would play 36. h7!) 36. h4 Kd7 37. a4 f6 38. exf6 Ke6 39. h5

Black cannot break through. Draw! Notice that if Black did not have his own a5 pawn, he would be winning – this actually happened a bit later in that same game.

Instead of allowing such a fortress, Black should play 33… b3! 34.axb3 cxb3 35. Kd1 Na3 36.Kc1 Nc4 –+

Full domination of knight over bishop.