Now the picture is clear. Black cannot even prevent White from winning back a pawn on a5 .

In reality, exchanging is not about what is taken from the board, but more about what is left on the board. After an exchange of queens the strength of the remaining pieces may come to the fore, yielding a pleasant endgame.

White is hoping to use the a- and c-files for his rooks. The doubling of pawns on the way can make it harder for you to detect this possibility, though there are some famous precedents, for example, Smyslov-Tal, Bled 1959.

Otherwise Black would play . . . Na7-b5 .

And eventually White managed to squeeze out a win.

When exchanging a piece you can try to eliminate an active piece of your opponent, but when attacking you can also try and remove one of your opponent's strongest defensive pieces. So what would you play in the diagram position?

The difficulty here is maybe that, when conducting an attack on the king, you are disinclined to opt for an exchange of queens. Yet in this case, Black's attack continues with great force. The pawn on g2 is deprived of a defender and ... h4-h3 is a nasty threat.