1.Bf1+ wins Qe2/d3 is clearly useless and Ka5 allows Qxa7 ++ , so Black plays Rb5. White replies 2.a4 to re-inforce the pin and it’s game over – “spite check” Rxg3 prolongs the game by one move but cannot save Black.
I don’t know if it is the most efficient, but Bf1 is what I would play here:
1. Bf1 Rb5 (Ka5 2.Qa7#) 2. Qe6
No real reason for this choice other than the threat of Rxb5 (c-pawn is pinned). Now black can play Ka5 or Kb7 before or after sacrificial delays:
2. …..Kb7 3. Qd7 Kb8 (quick mate otherwise) 4. Rb5 cb5 5. c6 and the mate can only be delayed, not prevented.
Or, at move 2:
2. …..Ka5 3. Qc6!
And with the threat of Qa6# if black takes at b1, I again see only sacrificial delays to the ultimate mate. Rb6 guards the a6 square, but mate still follows:
Now, like I wrote, black can delay things with various sacrifices like Qf2 and Rg3, but right now I can’t see a shorter line than the ones I have outlined.
1. Bf1+ Rb5 2. a4 looks obvious and it wins the sacrificed R back, with a good position. But I think 2. Qd7 is better, threatening, among other things, 3. Q:c6+ and 3. B:b5+ cb 4. Q:b5#. I don’t think there’s anything Black can do except give away wood to delay mate.
Most efficient seems indeed to be CraigB’s suggestion. It’s advantage over my suggestion is that it prevents Kb7 by black. Hard to be sure of all of the sacrificial delays without playing them all out, but I count a mate in 10 in what looks to be the longest line for black.
Bf1+. Took me more than five seconds.
1) bf1+, rb5 (if ka5, qxa7#)
2) bxr5+, pxb5
3) qxr
Bf1+ Ka5 Qxa7#
Bf1+ Rb5 Qxg8 seems the safest.
Bf1+ Rb5 a4 also possible
1.Bf1+ wins
Qe2/d3 is clearly useless and Ka5 allows Qxa7 ++ , so Black plays Rb5.
White replies 2.a4 to re-inforce the pin and it’s game over – “spite check” Rxg3 prolongs the game by one move but cannot save Black.
Let us see now…
how about
1. Bf1+ Ka5 (can be delayed by
offering Qe2?)
2. Qxa7#
?
Is it really this simple?
Bf1+
1 Bf1+ Rb5
2 a4
Winning
I don’t know if it is the most efficient, but Bf1 is what I would play here:
1. Bf1 Rb5 (Ka5 2.Qa7#)
2. Qe6
No real reason for this choice other than the threat of Rxb5 (c-pawn is pinned). Now black can play Ka5 or Kb7 before or after sacrificial delays:
2. …..Kb7
3. Qd7 Kb8 (quick mate otherwise)
4. Rb5 cb5
5. c6 and the mate can only be delayed, not prevented.
Or, at move 2:
2. …..Ka5
3. Qc6!
And with the threat of Qa6# if black takes at b1, I again see only sacrificial delays to the ultimate mate. Rb6 guards the a6 square, but mate still follows:
3. …..Rb6
4. Rb5 Ka4 (Ka6 5.Rb6)
5. Rb4 with 6.Qa4# unstoppable
Now, like I wrote, black can delay things with various sacrifices like Qf2 and Rg3, but right now I can’t see a shorter line than the ones I have outlined.
bf1+
1. Bh3-c8+
–br
1.Bf1+
And black has to block with rook or queen and white regains some material.
1…Rb5 2.a4 attacking the pinned rook.
If 1…Ka5 2.Qxa7#
Might not be the best continuation for white.
1. Bf1+ Rb5 2. a4 looks obvious and it wins the sacrificed R back, with a good position. But I think 2. Qd7 is better, threatening, among other things, 3. Q:c6+ and 3. B:b5+ cb 4. Q:b5#. I don’t think there’s anything Black can do except give away wood to delay mate.
Most efficient seems indeed to be CraigB’s suggestion. It’s advantage over my suggestion is that it prevents Kb7 by black. Hard to be sure of all of the sacrificial delays without playing them all out, but I count a mate in 10 in what looks to be the longest line for black.