1.
[{B:q7/n2BNp2/5k1P/1p5P/1p2RP2/1K6/8/8}
{V:White to play and mate in six. Try your solution on the board.;e4e3;Correct;
Incorrect.;Black's queen has the responsibility of covering the potential mates by Ng8 and Nd5. This means that if it were Black to move, then he would have to allow mate in one, because any queen move loses control of one of the two critical squares, while a knight move necessarily obstructs the queen. However, White cannot maintain the status quo, and in fact he has few reasonable moves himself, since he cannot allow Black to start checking. This means that it should be possible to find the solution by a process of elimination.}]

2.
[{B:q7/n2BNp2/5k1P/1p5P/1p2RP2/1K6/8/8}
This is a curious position in which both sides are in a straitjacket. There are potential mates by Nd5 and Ng8, so Black's queen must maintain control of d5 and g8. This means that Black to move would have to allow immediate mate, since the queen cannot retain control of both squares, while a knight move would block the queen. It follows that a waiting move would force immediate mate, but White has no waiting moves available, for example 1 Kb2? b3, with ...b4 and ...Nb5 to come, or 1 Bg4? (or Bh3?) Qd8! (White's bishop move opened up the line d8-d5) threatening ...Qxe7.]

3.
[{B:q7/n2BNp2/5k1P/1p5P/1p2RP2/1K6/8/8}
{S:e4e3}
1 Re3!
Just about the only reasonable move. We have seen that the bishop and king cannot move, and White cannot allow ...Qf3+, so Re3 it is.]

4.
[{B:q7/n2BNp2/5k1P/1p5P/1p3P2/1K2R3/8/8}
{S:a8g2}
1...Qg2
This is why Re3 isn't an effective waiting move, Black's queen is given an alternative square from which to guard d5 and g8. Now Black threatens to disrupt the mating net completely by playing ...Nc6, so White must act quickly.]

5.
[{B:8/n2BNp2/5k1P/1p5P/1p3P2/1K2R3/6q1/8}
{S:d7g4}
2 Bg4
Cutting Black off from g8. Now 2...Qxg4 fails to 3 Nd5+ Kf5 4 Re5 mate, so Black's queen must rush back to the corner.]

6.
[{B:8/n3Np2/5k1P/1p5P/1p3PB1/1K2R3/6q1/8}
{S:g2a8}
2...Qa8
The situation differs from that at move one because White's bishop covers f3, so his rook is free to move off the third rank without allowing ...Qf3+.]

7.
[{B:q7/n3Np2/5k1P/1p5P/1p3PB1/1K2R3/8/8}
{S:e3e5}
3 Re5!
Black is again seriously short of moves. 3...Qf3+ allows 4 Bxf3 followed by a knight mate, and the knight cannot move, so the queen must continue her journeys.]

8.
[{B:q7/n3Np2/5k1P/1p2R2P/1p3PB1/1K6/8/8}
{S:a8d8}
3...Qd8
Threatening ...Qxe7, or a check on the d-file, but White has a reply which not only meets these threats, but also gently tightens the net around Black's king.]

9.
[{B:3q4/n3Np2/5k1P/1p2R2P/1p3PB1/1K6/8/8}
{S:g4d7}
4 Bd7
Black cannot play 4...Qxe7 because of 5 Rf5 mate, so again the queen has no choice.]

10.
[{B:3q4/n2BNp2/5k1P/1p2R2P/1p3P2/1K6/8/8}
{S:d8a8}
4...Qa8
But now White reveals the point behind all his maneuvers ...]

11.
[{B:q7/n2BNp2/5k1P/1p2R2P/1p3P2/1K6/8/8}
{S:e5e4}
5 Re4
This returns to the initial position, but with Black to move instead of White. As we mentioned at the start, this means that White can mate next move. The white rook was the hero of the solution, since the round trip Re4-e3-e5-e3 was the key loss of tempo, but the bishop's outing to g4 and back again was the catalyst that made the whole thing work. Black's poor queen deserves some sympathy; she ran back and forth trying to hold Black's position together, but all to no avail.]
