1.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8}
{V:White to play and mate in four. Try your solution on the board.;b7a6;Correct;
Incorrect.;Black's main defense is to run away with his king by ...Kc4. This must be prevented, even at the cost of extreme measures.}]

2.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8}
{S:d7d6}
Try 1 Kd6? Nf6 (but not 1...Ng5? 2 Ba5+ Kxa5 3 Kc6 and mates by Qb5) 2 Ba5+ Kc4 and now there is no mate on d5.]

3.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8} 
{D:100}{S:b6d4}
Try 1 Bd4+? Kc4 and the king slips away.]

4.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8}
{D:100}{S:b7c6}
Try 1 Qc6+? Kb4 and there is no mate.]

5.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8}
It is tempting to give a check with the bishop, but this would certainly be an unusually brutal start to a problem. In fact the bishop checks don't lead to mate, as Black replies ...Kc4. Most quiet moves fail because Black starts checking with his knight, delaying the mate beyond move four. If White avoids the knight checks by 1 Kd6, Black replies 1...Nf6! 2 Ba5+ Kc4 (not 2...Kxa5 3 Kc6) and the knight stops mate on d5, so the king escapes. This is a 'lateral thinking' type of problem, the solution can only be found by overcoming one's normal chess inhibitions.]

6.
[{B:8/1Q1K3n/1B6/1k6/8/8/1P6/8}
{S:b7a6}
1 Qa6+!
Problems less than six moves long rarely start with a check, so when a composer does incorporate a checking first move, it can be quite hard to find. Moreover, in such a simplified position there is a natural reluctance to part with White's most powerful piece.]

7.
[{B:8/3K3n/QB6/1k6/8/8/1P6/8}
{S:b5a6}
1...Kxa6
After  1...Kb4 2 Qd3 Black cannot prevent 3 Kc6 followed by 4 Qb5 mate.]

8.
[{B:8/3K3n/kB6/8/8/8/1P6/8}
{S:d7c6}
2  Kc6!
Now White's king is out of the black knight's range and there is no way to prevent 3 b4 and 4 b5 mate.]
