Exchanging pieces down to win

When deciding to take pieces, it's always good to remember "to take is a mistake" unless a trade improves your position or worsens your opponent's position, or if you win material.

You want to always have a good reason to make exchanges. One great reason to exchange pieces is when you are ahead in material. In that case trades will simplify the game and make it easier for you to convert your advantage into a win. But if you have less material, you should never trade pieces.

Future World Champion Mikhail Botvinnik has the Black pieces. Can you find his winning idea to trade down into a winning position?

Botvinnik trades down to win! What is the correct pawn move to win the game for Black?

White is helpless against Black's plan to play ...b2 on the next turn when Black will win the game.