I don’t know if this is the shortest mate, but this at least works:
1. Bc6 Kb8 2. Re7
The only 7th rank moves to avoid here is Rd7 and Rb7/a7. None of them fail to mate, I think, but you will have to backtrack to do so- at d7 the rook is taken by the bishop if black discovers by moving the bishop off of c7 at move 4 below:
Bc6+ looks very obvious, but is this a pitfall? I am only able to see delaying sacks by black from here, but white needs to continue accurately, there must be only one choise for black at each move:
1. Bc6+ Kb8 2. Rb7++ Ka8 (gives white a tempo by discovered check) 3. Rh7+ Rc7 (first sack, king couldn’t move) 4. Rh8+! Bc8 (only move, Ka7 Ra8#) 5. Bxc7+ Ka7 6. Rxc8 and Ra8# can’t be guarded, white bishops are ideally set up. Note that black’s two sacks were not taken inmmediately, there was a better move to do first. 6. … Rxb2+ 7. Kxb2 Bd4+ 8. Kb3 h1=Q 9. Ra8#
Correction!! Please leave out my suggested odd 2. move Rb7+?? Ka8!! As you may see, the rest of my line also was calculated without this move, I had king on b8 so I could play Bxc7 with check. So it is: 1. Bc6+ Kb8 2. Rh7+ Rc7 3. Rh8+ Bc8 4. Bxc7+ Ka7 5. Rxc8 and mate in 3 more moves.
I don’t know if this is the shortest mate, but this at least works:
1. Bc6 Kb8
2. Re7
The only 7th rank moves to avoid here is Rd7 and Rb7/a7. None of them fail to mate, I think, but you will have to backtrack to do so- at d7 the rook is taken by the bishop if black discovers by moving the bishop off of c7 at move 4 below:
2. …..Rc7
3. Bc7 Ka7 (Kc8 4.Re8#)
4. Bd6 Bd7
5. Rd7#
Fc6+_Kb8
Rb7+_Ka8
Nc7+_R*Nc7
R*Rc7+_Kb8
Rb7+_(Kc8;Rb8#)
Ka8
Rb8+_Ka7
Ra8#
1-0
This seems straight forward though I’ve been wrong…
Bc6+ (Nxb6+ Bxb6) Kc7 Rh7+ Rc7 Bxc7+ (Rh8+ right away Bc8 makes it tougher) Ka7 (Kf8 Rh8#) Bd6+ Bd7 Rxd7#
LegalEagle says:
1.Bc6+ Kb8
2.Re7+ Rc7
3.Bxc7+ Ka7 if …. Kc8
4.Bd6+ Bd7 4.Re8#
5.Rxd7#
1. Bc6+ Kb8
2. Rb7+ Ka8
3. Nc7+ Rxc7
4. Rxc7+ Kb8
5. Rb7+! (important to give a double check here) .. Ka8
6. Rd7#
1.Bc6+Kb8 2.Rh7Rc7 3.Bc7Ka7 (3. … Kc8 4.Rh8#) 4.Bd6Bd7 5.Rd7#
1. Bc6+ Kb8
2. Rh7+ Rc7
3. Bxc7+ Kc8 (Ka7 4. Bd6++)
4. Rh8++
1.Bc6+ Kb8
2.Rb7+ Ka8
3.Nc7+ Rxc7
4.Bxc7
and I don’t see any defense for black for the white’s ensuing mate threat – Rb8+ and Ra8#
1-BC6+ -KB8 2-RB7+ KA8 3-RB7+ MAT
1. Bc6+ Kb8
2. Re7+ Rc7
3. Bxc7+
from here, the king can choose to go to a7 or c8.
3…….. Ka7
4. Bxh2+ (or anywhere along the c7-h2 diagonal) Bd7
5. Rxd7#
OR 3 ….. Kc8
4. Re8 #
Mate in five:
1. Bc6+ Kb8
2. Rb7++ Ka8
3. Nc7+!
The black rook must be diverted from the 8th rank.
3. … Rxc7
4. Rb8++ Ka7
5. Ra8#
i think it should be something like
1. Bc6+ Kb8
2. Re7+ Rf7
3. Bxc7+ Ka7 (Kc8, 4. Rf8#)
4. Bd6+ Bd7
5. Rxd7#
greets, jan
1. Bc6+ , Kb8
2. Rb7+ , Ka8
3. Nc7+ , Rxc7
4. Rxc7+, Kb8
5. Rb7+
Two options for black
5. …. , Ka8
6. Rb8+ , Ka7
7. Ra8#
and
5. …. , Kc8
6. Rb8#
Greetongs from Spain
1.Bc6+ Kb8 2.Re7+ Rc7 3.Bxc7+ if Kc8 4.Re8# if 3…Ka7 4.Bd6+ Bd7 5.Rxd7#
Bc6+ looks very obvious, but is this a pitfall?
I am only able to see delaying sacks by black from here, but white needs to continue accurately, there must be only one choise for black at each move:
1. Bc6+ Kb8
2. Rb7++ Ka8 (gives white a tempo by discovered check)
3. Rh7+ Rc7 (first sack, king couldn’t move)
4. Rh8+! Bc8 (only move, Ka7 Ra8#)
5. Bxc7+ Ka7
6. Rxc8
and Ra8# can’t be guarded, white bishops are ideally set up.
Note that black’s two sacks were not taken inmmediately, there was a better move to do first.
6. … Rxb2+
7. Kxb2 Bd4+
8. Kb3 h1=Q
9. Ra8#
1. Bc6+, Kb8 2. Re7+, Rc7 3. BXc7+,Ka7 4. Bd6# OR (Kc8; Re8#)
Correction!!
Please leave out my suggested odd 2. move Rb7+?? Ka8!!
As you may see, the rest of my line also was calculated without this move, I had king on b8 so I could play Bxc7 with check. So it is:
1. Bc6+ Kb8
2. Rh7+ Rc7
3. Rh8+ Bc8
4. Bxc7+ Ka7
5. Rxc8 and mate in 3 more moves.
Black has committed the fatal mistake of pushing a rook pawn to the 2nd rank. White wins by checking until it is mate, starting with Bc6+.
1.Bc6 check Kb8 2. Rb7check Ka8 3. Nc7Check Rxc7 and then 4. Rb8+ Ka7 5. Finally should Ra8 mate
Bc6+ Kb8
Rf7+ Rc7
Bxc7+ Kc8
Ne7+ Kd7
Nxf5 Pxf5
Rxf5 and Black can resign.
1-bc6+/kb8 2-RB7+/ka8 3-RB8+ MAT
1.Bac6+ Kb8
2.Rxc8+ Ka7
3.Ra8#