BPCF 2019 - XIV Београдски фестивал проблемског шаха 2019.
Belgrade Internet Tournaments 2019
Group A – #2 , Mate in two moves
Judge:
Dr. Paz Einat, International Judge
Director:
Marko Ložajić
It was an interesting idea by Marjan Kovačević to use the 4-phase reciprocal changes theme, which I promoted
in the last couple of years, as a theme for this year’s Belgrade Internet Tourney. My hunch was that much can be
done, but only after receiving the 17 anonymous problems from the director, Marko Ložajić, I could see that my hunch
was correct.
The problems presented a good variety of mechanisms realizing the theme. My clear preference was for mechanisms that
are purely 4-phase ones. One problem had a 2-phase mechanism and two others had 3-phase mechanisms, in both cases
somewhat artificially spread onto four phases. Such adaptation should not be dismissed, they can be of interest,
but I gave them lower preference.
The 4-phase requirement gave rise to mechanisms based solely on separation of defenses by the threats. This means that
both defenses would give rise to the same thematic mate but the threats determine that only one is a real defense.
Such mechanisms has a definite taste of artificiality, but in some way, they might look rather humoristic. I gave
these the lowest preference but I did not dismiss them altogether.
Now to the award. Grading the problems was not an easy task and the differences between the problems were small.
In addition to the thematic requirement, I used a variety of criteria and tried to weigh clarity versus complexity and
the importance of additional element.
Thematic condition
4-phase reciprocal changes
Reciprocal changes of two mates, spread over 4 phases, according to the pattern presented in the examples.
Example 1
Paz EINAT
3rd HM, The Problemist 2017
white Bh7g1 Ka8 Qa2 Pc6a4b4d4 Sb7f3 Re7a6
black Qe3 Pc7d7h6e5c4d3d2 Kd5 Ba5 Rh4
#2
(12+11)
1.Sb7-c5 ? threat: 2.Re7*d7 #
1...d7-d6 {a} 2.Bh7-g8 # {A}
but 1...Ba5-b6 !
1.Sf3*e5 ? threat: 2.Qa2*c4 #
1...Rh4*d4 {b} 2.Ra6*a5 # {B}
but 1...Qe3*d4 !
1.Sb7-d8 ? threat: 2.Re7*d7 #
1...d7-d6 {a} 2.Ra6*a5 # {B}
but 1...Ba5*b4 !
1.Sf3*d2 ! threat: 2.Qa2*c4 #
1...Rh4*d4 {b} 2.Bh7-g8 # {A}
1...Qe3*d2 2.Re7*e5 #
1...Qe3*d4 2.Bh7-g8 #
Example 2
Paz EINAT
1st Pr. Israel QCT 2017
white Bd1 Kc1 Qd6 Pd4f4b3f3 Se2g2 Rg5
black Qh6 Pa6b5f2 Kd3 Bb8g6 Se1
#2
(10+8)
1.Rg5-c5 ? threat: 2.Rc5-c3 #
1...Qh6*f4 + {a} 2.Se2*f4 # {A}
but 1...Se1*f3 !
1.Qd6-e6 ? threat: 2.Qe6-e3 #
1...Bb8*f4 + {b} 2.Sg2*f4 # {B}
but 1...Bb8-e5 !
1.Rg5-e5 ? threat: 2.Re5-e3 #
1...Qh6*f4 + {a} 2.Sg2*f4 # {B}
but 1...Bg6-e4 !
1.Qd6-c5 ! threat: 2.Qc5-c3 #
1...Bb8*f4 + {b} 2.Se2*f4 # {A}
Example 3
Мarjan Kovačević
3rd Pr. Die Schwalbe 1983
white Qc6 Sf7b3 Re8a4 Be1 Kh1
black Pc7h6c3 Sd5h2 Ba8a1 Kf3
#2
(7+8)
1.Qc6-b5 ? threat: 2.Qb5-e2 #
1...Sd5-e3 {a} 2.Sf7-e5 # {A}
but 1...Sd5-f4 !
1.Qc6-d7 ? threat: 2.Qd7-h3 #
1...Sd5-f4 {b} 2.Sb3-d4 # {B}
1...Sh2-g4 2.Qd7*g4 #
but 1...Sd5-e3 !
1.Re8-e4 ? threat: 2.Sf7-e5 #
1...Sd5-e3 {a} 2.Sb3-d4 # {B}
but 1...Sh2-g4 !
1.Ra4-e4 ! threat: 2.Sb3-d4 #
1...Sd5-f4 {b} 2.Sf7-e5 # {A}
1...c3-c2 2.Sb3-d2 #
Winners
Anatoly Vasilenko
Mark Basisty
Vasil Markovcij
Mihail Hramtsevich
Dragan Stojnić
Participants
Mark Basisty – UKR (1,7*)
Hubert Gockel – GER (2,8)
Mihail Hramtsevich – BLR (4*,9*)
Zoltán Labai – HUN (3*)
Vasil Markovcij – UKR (4*,9*)
Miodrag Mladenović – SRB (11)
Pavel Murashev – RUS (5,10)
CGS Narayanan – IND (12,16)
Vyacheslav Pilchenko – RUS (6*,13*)
Valery Shanshin – RUS (6*,13*)
Dragan Stojnić – SRB (14,17)
Gábor Tar – HUN (3*)
Anatoly Vasilenko – UKR (7*)
Daniel Wirajaya – INA (15)
14 names
from 8 countries
BPCF2019A - Award
1st Prize
Anatoly Vasilenko & Mark Basisty, UKR
white Qh5 Pb3a3b2f2f4h3c6 Ka5 Bh8 Sf5d8
black Pb5c7d6d5d3f7 Kc5 Rg7
#2
(12+8)
Set: 1...d4 2.??
1.Qf3? zz 1...d4 a 2.Sb7# A
1...d2 2.Qc3# 1...R~ 2.Bd4# 1...b4 2.axb4# but: 1...f6!
1.Se3? [2.Qxd5#] 1...Rg5 b 2.b4# B
(1...Kd4 2.Qxd5#) but: 1...f5!
1.Qxf7? zz 1...d4 a 2.b4# B
1...R~ 2.Bd4# 1...b4 2.axb4# but: 1...d2!
1.Se7! [2.Qxd5#] 1...Rg5 b 2.Sb7# A
1...f5 2.Se6# (1...Kd4 2.Qxd5#)
(1.Qd1? [2.Qc1#] 1...d2 2.Qc2# 1...Rg1 2.Bd4# but: 1...d4!)
A very clear 4-phase mechanism. In two phases, we have line opening by BPd5 once to c6 and once to c4, enabling, alternatively, the Sb7 & b4 mates. In the other two phases, we have flight provision on d4 by the keys, which guard either c6 or c4. Thus, the line opening by the BR-defense, guarding the d4 flight, enable the same two mates. In these two phases, one can argue that 1...d4 would also self-block on d4 and enable the mates (it is prevented by the pin), but this is incidental and not part of the mechanism. Good additional mate changes and the use of both waiting and threats shows the flexibility of the composers.
FEN: 3N3B/2p2pr1/2Pp4/Kpkp1N1Q/5P2/PP1p3P/1P3P2/8
(C+ by Popeye)
2nd Prize
Vasil MARKOVCIJ & Mihail HRAMTSEVICH, UKR
white Bh2g2 Ka7 Qa1 Pf5d6c3 Se3 Rh7
black Pc4c5c6d7f6 Ke5 Sf4d3
#2
(9+8)
1.Rh4? zz 1...S~ a 2.Bxf4# A, but: 1...Kxd6!
1.Qa5? zz 1...S~ a 2.Qxc5# 1...Kxd6 b 2.Sxc4# B
but: 1...Sb4!
1.Qb1? zz 1...S~ a 2.Sxc4# B 1...Kxd6 b 2.Qb8#
but: 1...Sb2!
1.Qd1! zz 1...S~ a 2.Re7# 1...Kxd6 b 2.Bxf4# A
The 4-phase reciprocal changes mechanism is not as clear as in the 1st Prize problem, but there is a 3x2 Zagoruiko involving the thematic defenses. Both Sxc5 & Bxf4 mates can be given after 1...Kxd6 provided that the right squares are guarded and (for Bxf4) that BSd3 is pinned. For the mates after the 1...S~ defense, Sxc5# requires guard of f5 and Bxf4# guard of f4. The three try and key moves provide these to drive the reciprocal changes. The refutations of the 2nd & 3rd tries are excellent, and the way the composer managed the additional mates completing the Zagoruiko is admirable.
FEN: 8/K2p3R/2pP1p2/2p1kP2/2p2n2/2PnN3/6BB/Q7
(C+ by Popeye)
3rd Prize
Dragan STOJNIĆ, SRB
white Bh7h6 Kc1 Qb3 Pf6c6c2 Se6b5 Rd5
black Bb7 Ke4 Qf7 Pe7b6f5h4d4b4a3g3 Sg6 Ra5g4
#2
(10+14)
Set: 1...S~ 2.Bxf5#, 1...Se5! (2.Bf5?)
1.Sexd4? [2.Qf3#] 1...Qxd5 a 2.Qe3# A
1...Se5 2.Bxf5# but: 1...Rf4!
1.Sbc7? [2.Qd3#] 1...Rxd5 b 2.Qxd5# B
1...Se5 2.Rxd4# 1...Sf4 2.Bxf5# but: 1...Ba6!
1.Sec7? [2.Qd3#] 1...Qxd5 a 2.Qxd5# B
1...Se5 2.Rxd4# 1...Sf4 2.Bxf5# but: 1...Rg5!
1.Sbxd4! [2.Qf3#] 1...Rxd5 b 2.Qe3# A
1...Se5 2.Bxf5# 1...Rf4 2.Sg5#
(1.Bf4? [2.Rxd4#] 1...d3 2.Qxd3# 1...Sxf4 2.Bxf5#
1...Rxf4 2.Sg5# but: 1...Qxf6!)
The two black lines mechanism, first shown by one of my problems, is adapted here in a very nice and different way. The 1st moves by the WS’s either guard d5, and enable the mate on d5, or capture d4 and enable the self-block on d5 to be exploited by the Qd3 mate. Nice and clear! The composer neatly used the matrix to devise two different refutations on the tries on c7 and the additional Dombrovskis element, with the mate change on 1...Se5, is a good addition
FEN: 8/1b2pq1B/1pP1NPnB/rN1R1p2/1p1pk1rp/pQ4p1/2P5/2K5
(C+ by Popeye)
1st Hon. Mention
Vasil MARKOVCIJ & Mihail HRAMTSEVICH, UKR
white Bg5a8 Ka7 Qa1 Pe3f5d6c6 Sc3e7 Re8
black Pc4c5 Ke5 Sd3
#2
(11+4)
1.Qd1? zz
1...Kxd6 a 2.Bf4# A 1...S~ b 2.Qd5#
1...Sf4 2.exf4# but 1...Sb4!
1.Qb1? zz
1...Kxd6 a 2.Qb8# 1...S~ b 2.Sc8# B, but 1...Sf4!
1.Qa5? zz
1...Kxd6 a 2.Sc8# B 1...S~ b 2.Qxc5#, but 1...Sb4!, Sf4!
1.Rf8! zz 1...Kxd6 a 2.Sb5# 1...S~ b 2.Bf4# A
The ideal way of showing the 4-phase reciprocal changes in the format of a 4x2 Zagoruiko. This problem, which is a version of the 2nd Prize by the same author, incredibly achieved this task! The price paid are two refutations on the 1.Qa5? try. One can regard this as “refutation separation”, as the next two tries have these refutations individually, but I see it as a weakness. Also, WBa8 is unused in the solution. The mechanism is different enough for the problem to stand on its own, in principle due to the use of the WQ/WS & WR/WS batteries.
FEN: B3R3/K3N3/2PP4/2p1kPB1/2p5/2NnP3/8/Q7
(C+ by Popeye)
2nd Hon. Mention
C.G.S. NARAYANAN, IND
white Bh1e1 Ka8 Qc2 Pc6g6e3b4a3 Sd4 Re6h6
black Pc7d6h3h2e5a4 Kd5 Rg2
#2
(12+8)
1.Bg3? zz 1...e4 a 2.Rh5# A
but 1...exd4 b !
1.Kb7? zz 1...exd4 b 2.Qa2# B, but 1...e4 aa !
1.Bf2? [2.e4#] 1...e4 a 2.Qa2# B, but 1...exd4!
1.Rf6! zz
1...exd4 b 2.Rh5# A 1...e4 a 2.Rf5#
(1.g7? zz 1...exd4 2.e4# but 1...e4!)
The problem probably shows the most original mechanism. The moves by BPe5 both guard e4 and open the 5th row. However, 1...e4 prevents both thematic mates due to the unpin of BRg2, and 1...exd4 prevent them by unguarding c6 and e6. The tries and key either make an interference of the BR lines or guard c6 & e6 (separately). The mate change on 1...e4 in the solution is good but the repetition of the refutation is a weakness
FEN: K7/2p5/2PpR1PR/3kp3/pP1N4/P3P2p/2Q3rp/4B2B
(C+ by Popeye)
3-4th Hon. Mention
Mark BASISTY, UKR
white Bh2 Kb5 Qd3 Pc2g6 Sf5h5 Rd8g3
black Qc1 Ke5 Pg7e2e3g4h4e6b3 Sd7h6 Bf4
#2
(9+12)
(1.Se7? [2.Sc6#] 1...Sb8 2.Qd4# 1...Qxc2 2.Rxe3#, but 1...Qh1!)
1.Rxg4? [2.Bxf4#] 1...Bxh2 a 2.Qe4# A
1...Bg3 2.Qe4# 1...exf5 2.Re8# but 1...Qf1!
1.Sxe3? [2.Sc4#] 1...Sb6 b 2.Qd4# B
1...Bxe3 2.Rxe3# 1...Qxe3 2.Rxe3# but 1...Qxc2!
1.Rf3? [2.Bxf4#] 1...Bxh2 a 2.Qd4# B
1...Bg3 2.Qd4# 1...exf5 2.Re8# but 1...g3!
1.Sd6! [2.Sc4#] 1...Sb6 b 2.Qe4# A
1...Qxc2 2.Rxe3#
The mechanism is from the same type as that of the 1st Prize but with a twist. The tries by the WR open guard on f5 or e4 after the BB defense, leading to the thematic mates. In the 3rd try WSf5 provides guard on f5 alone, enabling the Qd4 mate after the defense by BSd7, while the solution provides guards on both f5 & e4 but closes the d-file for the WR thus preventing the guard on d4 by the defense move.
FEN: 3R4/3n2p1/4p1Pn/1K2kN1N/5bpp/1p1Qp1R1/2P1p2B/2q5
(C+ by Popeye)
3-4th Hon. Mention
Zoltán LABAI & Gábor TAR, HUN
white Ba8c3 Ka2 Qh1 Pe4d2 Se5f4 Rb1
black Bg1 Kc2 Qh4 Pc7a3g3b2 Sh3a1 Re7g5
#2
(9+11)
1.Sf3? [2.Se1#] 1...Rxe4 a 2.Bxe4# A
1...Bf2 2.Qd1# but 1...g2!
1.Sd5? [2.Sb4#] 1...Qxe4 b 2.Qxe4# B
1...Bc5 2.Qd1# but 1...c5!
1.Sc6? [2.Sb4#] 1...Rxe4 a 2.Qxe4# B
1...Bc5 2.Qd1# but 1...Rb5
1.Sg2! [2.Se1#] 1...Qxe4 b 2.Bxe4# A
1...Bf2 2.Qd1#
(1.Sfd3? [2.Se1,Sb4#] but 1...Qxe4!
1.Sed3? [2.Se1,Sb4#] but 1...Rxe4!)
Another way to express the two black lines mechanism (see 3rd Prize). The moves by the WS’s either close the WQ or WB while opening the BQ or BR lines. Therefore, these are a kind of bi-color valve moves. The board geometry is nicely used for the WS threats, the additional tries on d3 feature the thematic defenses as refutations, and the refutations on the thematic tries are all fine.
FEN: B7/2p1r3/8/4N1r1/4PN1q/p1B3pn/KpkP4/nR4bQ
(C+ by Popeye)
5th Hon. Mention
Pavel MURASHEV, RUS
white Bg8e5 Kh6 Qg3 Pd6c3e2 Sb8c2 Rb5d1
black Pf7b6f6c5c4e4e3 Ke6
#2
(11+8)
1...fxe5 a 2.Qg6# A
1.Sxe3? zz 1...fxe5 a 2.Qg6# A
but 1...f5!
1.Rd5? zz 1...fxe5 a 2.Qxe5# B
1...Kxd5 2.Bxf7# 1...Kf5 2.Qh3# but 1...f5!
1.Bd4? zz 1...f5 b 2.Qe5# B
1...Kd5 2.Bxf7# 1...cxd4 2.Sxd4# but 1...Kf5!
1.Bf4! zz 1...f5 b 2.Qg6# A
1...Kf5 2.Sd4#
A very nice mechanism, using the set play as one of the phases. The WQ will mate on g6 or e5 (if free and guarded) following defenses by BPf6. Determinants are the flight on d5 and blocking the WQ towards e5. It would have been nice to have the flight-giving 1.Bd4? try as the solution. Overall, there are additional mate changes and a mate transfer.
FEN: 1N4B1/5p2/1p1Pkp1K/1Rp1B3/2p1p3/2P1p1Q1/2N1P3/3R4
(C+ by Popeye)
6th Hon. Mention
Vyacheslav PILCHENKO & Valery SHANSHIN, RUS
white Bb8g2 Kc5 Qb5 Pf7g7 Se6 Rh6e4
black Pe7g5c4 Kf5 Bb7f6 Sa2
#2
(9+7)
Set: 1...Bd4+ 2.Sxd4# 1...c3 2.Qf1#
1.Qb1? [2.Qf1#] 1...Be5 a 2.Rf4# A
1...Bd4+ 2.Sxd4# 1...Bxe4 2.Qxe4# but 1...Sc1!
1.f8=Q? [2.Sd4#] 1...g4 b 2.Re5# B but 1...Bxe4!
1.Qxc4? [2.Qf1#] 1...Be5 a 2.Rxe5# B
1...Bd4+ 2.Sxd4# 1...Bxe4 2.Qxe4# but 1...Ba6!
1.Qd7! [2.Sd4#] 1...g4 b 2.Rf4# A
The basic mechanism is well known from the 2-phase reciprocal changes (WQ on b1 for double check-mates on guarded squares and WQ on e2, guarding e6 & g4, with mates on unguarded squares). However, the use of the pinning try nicely takes this into the 4-phase realm.
FEN: 1B6/1b2pPP1/4Nb1R/1QK2kp1/2p1R3/8/n5B1/8
(C+ by Popeye)
1st Commend.
Pavel MURASHEV, RUS
white Bh6b1 Kc6 Qf7 Pd7f6c5f4h3 Se5e2 Re4e1
black Qd3 Pc7b5d5d4g3 Rg8b4 Bd8a2 Kf5
#2
(13+11)
Set: 1...Kxe4 a 2.Sxg3# A
1. Sc4? [2.Re5#] 1...Kxe4 a 2.Qxd5# 1...Qxe4 b 2.Sxd4# B
but 1...Re8, dxe4!
1. Sg4? [2.Re5#] 1...Qxe4 b 2.Sxg3# A
1...Re8 2.Qh7# but 1...dxe4, Kxe4!
1.Sf3! [2.Re5#]
1...Kxe4 a 2.Sexd4# B
1...Qxe4(/dxe4) b 2.Sh4# 1...Re8 2.Sxg3#
1. Sg6? [2.Re5#] 1...dxe4 2.Sh4#
(1...Qxe4 2.Sxg3, Sh4#) but 1...Kxe4, Re8!
The low place of this problem is due to the presence of two refutation in all tries. Other than this, the problem is rich in content and presents a pleasing mechanism. BK defense on e4 can lead to Sxg3 or Sxd4 depending on the need to guard f3 and the availability of a guard on d4. BQ capture on e4 leads to these mates depending on which of these squares were unguarded by interferences by WSe5. There is a 3x2 Zagoruiko plus additional changes, the defenses on the same square are nice and tries and key are by the same WS. Counting the non-thematic 1.Sg6 try, the double refutations show cyclicality, but this fact does not reduce the weakness inherent in them.
FEN: 3b2r1/2pP1Q2/2K2P1B/1pPpNk2/1r1pRP2/3q2pP/b3N3/1B2R3
(C+ by Popeye)
2nd Commend.
Vyacheslav PILCHENKO & Valery SHANSHIN, RUS
white Ba8h6 Kc1 Qh5 Pc2g4c4 Sd4e5 Rd1d5
black Be2h8 Ke4 Qb6 Pc5b4c3f6 Sg1e7 Rd8
#2
(11+11)
Set: 1...cxd4 a 2.R5xd4# A 1...fxe5 b 2.Rxe5# B
1.Rd3? [2.Re3#] 1...cxd4 a 2.R5xd4# A
1...Sxd5 2.Qf5# 1...Sf5 2.Qxf5# 1...Bxd3 2.cxd3# but 1...Rxd5!
1.Qh2? [2.Qf4#] 1...fxe5 b 2.Rxe5# B
1...Sh3 2.Qxe2# but 1...Sg6!
1.Sd3? [2.Sf2#] 1...cxd4 a 2.Re5# B
1...Bxd3 2.cxd3# but 1...Sh3!
1.Sf5! [2.Sg3#] 1...fxe5 b 2.R5d4# A
1...Sxf5 2.Qxf5#
This is, in principle, a 3-phase reciprocal changes problem since the captures, when both WS’s are on d4 & e5, can be done in one phase, and they exist as set play. Still, the WS try and solution are fine and the use of four different threats and three unique refutations make this a good composition.
FEN: B2r3b/4n3/1q3p1B/2pRN2Q/1pPNk1P1/2p5/2P1b3/2KR2n1
(C+ by Popeye)
3rd Commend.
C.G.S. NARAYANAN, IND
white Bh6b1 Kf7 Qh7 Pa7f2g3f5c6b4b3 Sf3 Rc2
black Pg4 Ke4
#2
(13+2)
1.a8=Q? zz 1...Kd5 a 2.Rd2# A
1...Kxf3 2.c7# 1...Kd3 2.f6# but 1...gxf3 b !
1.Be3? zz 1...gxf3 b 2.Rc5# B
1...Kd3 2.f6# 1...Kxf3 2.Qh1# but 1...Kd5 a !
1.Bf8? zz 1...Kd5 a 2.Rc5# B
1...Kd3 2.f6# 1...Kxf3 2.Qh1# but 1...gxf3 b !
1.Bf4! zz 1...gxf3 b 2.Rd2# A 1...Kd5 a 2.Rc5# B
1...Kd3 2.f6# 1...Kxf3 2.Qh1#
Another 3-phase mechanism extended into four. Here, both thematic variations exist in the solution (1...Kd5 a 2.Rc5# B 1...gxf3 b 2.Rd2# A) and together with the tries 1.a8=Q? and 1.Be3? we have 3-phase reciprocal changes. The additional phase does fulfil the required pattern and there are additional mate changes.
FEN: 8/P4K1Q/2P4B/5P2/1P2k1p1/1P3NP1/2R2P2/1B6
(C+ by Popeye)
4th Commend.
Hubert GOCKEL, GER
white Ba8 Kg7 Qf6 Pd6c5c3c2f2 Sf7c4 Rd3
black Pd7f3g5e5 Sb7b1 Rc6g2 Ke4 Bh2h5
#2
(11+11)
1.Sh6? [2.Qf5#] 1...Sxd6 a 2.Scxd6# A
1...Bg6 2.Qxf3# but 1...Bg4!
1.Scxe5? [2.Rd4#] 1...Rxd6 b 2.Sfxd6# B
1...Bxe5 2.Qxe5# 1...Rxf2 2.Sxg5# but 1...Sxc3!
1.Se3? [2.Qf5#] 1...Sxd6 a 2.Sfxd6# B
1...Bg4 2.Sxg5# but 1...Bg6!
1.Sfxe5! [2.Rd4#] 1...Rxd6 b 2.Scxd6# A
1...Sxc3 2.Sd2# 1...Bxe5 2.Qxe5#
This and the next two problems have mechanisms based on white threats. Here, a capture by both BRc6 and BSb7 on d6 leads to mates by both WS’s on d6 due to the half-pin. The separation elements involve the WS tries and key and the different threat that determine if the defense will be by the BR or BS. This is of course very artificial, and we do not really have reciprocal changes, but I find the ability to show the pattern in this way rather humoristic.
FEN: B7/1n1p1NK1/2rP1Q2/2P1p1pb/2N1k3/2PR1p2/2P2Prb/1n6
(C+ by Popeye)
5h Commend.
Miodrag MLADENOVIĆ, SRB
white Qd4 Pc7f6h5d5f2 Ka4 Rg2 Sd2
black Kf5 Pd7g7d6h4e3e2 Be8c1 Rf8h1
#2
(9+12)
1.Sf3? [2.Rg5#] 1...gxf6 a 2.Qg4# A
1...Rg1 2.Sxh4# but 1...exf2!
1.c8=S? [2.Sxd6#] 1...Rxf6 b 2.Qe4# B
but 1...Ba3!
1.f4? [2.Rg5#] 1...gxf6 a 2.Qe4# B
but 1...Rg1!
1.Sc4! [2.Sxd6#] 1...Rxf6 b 2.Qg4# A
1...Ba3 2.Sxe3#
(1.Rg4? [2.Qf4#] but 1...g5!
1.fxe3? [2.Qf4#] 1...g5 2.Rf2# but 1...Rf1!)
The tries and key leave one possible WQ mate following the self-block on f6. However, this mate can be given on both defenses and it is the threat that “prevents” one of them from being relevant.
FEN: 4brn1/2Pp2p1/3p1P2/3P1k1P/K2Q3p/4p3/3NpPR1/2b4r
(C+ by Popeye)
6th Commend.
Hubert GOCKEL, GER
white Bb1 Ke8 Qd8 Pe7e4 Sd6g4 Rc6b3
black Ph7a7b5c4 Kd4 Rd3 Bf1
#2
(9+7)
1.Kf7! [2.Qh8#] 1...Rf3+ a 2.Sf5# A
1.Qd7! [2.Qxa7#] 1...Rxb3 bB
1.Kd7! [2.Qh8#] 1...Rf3 a 2.Sxb5# B
1.Qa5! [2.Qxa7#] 1...Rxb3 bA
1...a6 2.Qb6#
As above, only one of the defenses works due to the threats. In two phases the battery remains and the double-check mate on the guarded squares is forced in different ways. In the other two phases the battery is inactivated and the mate can be given only on the unguarded squares. Using a 4-solutions approach is a simplification that I do not favor.
FEN: 3QK3/p3P2p/2RN4/1p6/2pkP1N1/1R1r4/8/1B3b2
(C+ by Popeye)
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