Solution to helpmate number 5

Both solutions show the theme of selected promotion of the pawn on e2. This is then followed by using the promoted piece to self-blocking a square or a line. In the first solution this is a square the black king could escape to on c2. In the second solution the first mate is prevented by the rook being able to move to e2. However, by moving to e4 black blocks the action of the bishop on f5 which would otherwise stop the mate by moving to c2. In each case these features assist white in achieving mate in the stipulated number of moves. Of course promotion to other pieces such as a queen or a bishop would not allow black to help white in this manner.

Solution 1

Black moving first:

1.e1=N Bg5 2. Nc2 Bf3 mate.

Solution 2.

Black moving first

1. e1=R Bg5 2. Re4 Bb3 mate.