1.
[
{B:n2Bqk2/5p1p/5KP1/p7/6Q1/8/8/8}
{V:White to play and win. Try to solve it on the board.;g4c8;Correct;Incorrect.;It is a shame to give any hint at all for this spectacular study, but I will reveal that White's second move is the big surprise. Black ends up with an enormous material advantage, but he is strangely helpless because of his dreadful king position.}]

2.
[
{S:g4c8}
1 Qc8!
Already an attractive move. 1 gxh7? would even lose after 1...Qxd8+ 2 Ke5 Qe7+ 3 Kd5 Qe6+ 4 Qxe6 fxe6+ 5 Kxe6 Kg7, but playing Qc8 sets up the threat of mate in two by 2 Be7+, so Black has no time to take the pawn on g6.]

3.
[
{S:f8g8}
1...Kg8
The only defense, because 1...Qe6+ 2 Qxe6 fxe6 3 gxh7 allows the pawn to slip through.]

4.
[
{S:d8c7}
2 Bc7!!
A truly incredible move. The only real alternative is 2 gxh7+ Kh8 3 Qxa8 Qe6+ 4 Kg5 Kxh7, but the ending of queen and bishop against queen is normally a draw, and here Black has two extra pawns to his credit. But why can't Black just make off with White's queen?]

5.
[
{S:e8c8}
2...Qxc8]

6.
[
{S:g6f7}
3 gxf7+]

7.
[
{S:g8h8}
3...Kh8
Forced, as 3...Kf8 allows mate in one by 4 Bd6.]

8.
[
{S:c7e5}
4 Be5
This is the position White was aiming for. He threatens mate in one by Ke7 or Kg5, and it doesn't help Black to push his h-pawn, because then White mates by Kg6 instead. Black's only defense is to attack the bishop on e5, and since his queen must retain control of f8, his reply is forced.]

9.
[
{S:c8c5}
4...Qc5
The attack on e5 has nullified the discovered checks, since 5 Ke6+, for example, is met by 5...Qxe5+ 6 Kxe5 Kg7 and Black wins easily. White must withdraw his bishop along the long diagonal in order to renew the mating threat, so the choice is between Ba1 and Bb2. Perhaps surprisingly, one move wins and the other loses. Which one is correct?]

10.
[
{S:e5b2}
5 Bb2!!
We will see later why 5 Ba1? loses. White has added the threat of Ke6 mate, Black's queen is already fully occupied dealing with the other king moves and covering f8, so he has to mobilise his last reserves.]

11.
[
{S:a8c7}
5...Nc7
An extraordinary position. Now Black cannot move his h-pawn (because of Kg6+), his knight (because of Ke6+) and his queen because of a king check or f8Q mate). Despite being a queen and a pawn up, the only thing he can move is his a-pawn.]

12.
[
{S:b2a1}
6 Ba1
White's movements are also restricted. He dare not allow Black to take the bishop with his queen, so he can only oscillate between b2 and a1.]

13.
[
{S:a5a4}
6...a4]

14.
[
{S:a1b2}
7 Bb2]

15.
[
{S:a4a3}
7...a3]

16.
[
{S:b2a1}
8 Ba1
Had White played 5 Ba1?, he would have arrived at this position with White to move. Since b2 is covered by the pawn, White would be dead lost. Black to play is forced to push his pawn, freeing b2 for the bishop.]

17.
[
{S:a3a2}
8...a2]

18.
[
{S:a1b2}
9 Bb2]

19.
[
{S:a2a1}{P:BQa1}
9...a1Q]

20.
[
{S:b2a1}
10 Bxa1
Black has run out of pass moves and must move one of his other pieces, allowing mate in at most three moves.]
