Originally posted by Kegge
I mean in the first solution rjhinds gave he mentions after move four it would be mate but for the Knight move. I don't think it is because the King can move to d3 ... so no mate in five and the remark about the Knight move is incorrect.
Yes, you are correct that the king can escape by 4...Kg3 in my first thoughts pgn where I say 4.Bf6+ would be checkmate if not for h7 knight. I overlooked that too.
However, I showed this thought mainly to show my first idea that led on to my finding the final solutions. This is were I first saw that the g7 bishop was in a bad place for a forced checkmate in 5 and that it would be better placed at d4 before I begin those checks with the rook, knight and the other bishop.
I showed this resulting idea in the second pgn with the g7 bishop relocated to d4 with White to move and demostrated the forced checkmate in 4 moves. I had already given up on the idea of a forced checkmate in 5 starting with the double-check move.
Then is when I decided that maybe the first move was Bd4 and began investigating what Black could do in response. From there I started eliminating Black responses until I got to 1...h1=N and realized my original plan had to be altered again.
The 3rd pgn shows the first real solution to the checkmate in 5 for 2...Nb3+ and the final pgn the solution in case of 2...Nc4.
I thought it might be of interest to others how I came about these weird looking beginning moves in this very difficult problem for me.