Chess Problems: Half-pin Blockbusters

2/12/2013 – In his previous articles on the half-pin theme our problem expert David Friedgood looked at a number of aspects of this fertile concept. There are many of other highways and byways of the theme that we could delve into. But David decided to say Auf Wiedersehen to the theme with a foursome of blockbusters, two of which the readers were invited to solve. Here are the the solutions.

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Half-pin Blockbusters

Report by David Friedgood

The first problem is a monumental achievement by the Serbian double GM for composing and solving, who, together with the Finn Kari Valtonen and other collaborators has recently brought out “Encyclopedia of Chess Problems: Themes and Terms” published by Chess Informant.

[Event "1st Prize Die Schwalbe"] [Site "?"] [Date "1986.??.??"] [Round "?"] [White "Milan Velimirovic"] [Black "Mate in 3"] [Result "*"] [Annotator "Friedgood,David"] [SetUp "1"] [FEN "3N2nB/1p3Prq/2pR1r1b/2P1kppR/2Pp4/3P3B/n2QPNK1/8 w - - 0 1"] [PlyCount "1"] [EventDate "1986.??.??"] 1. -- {This problem packs in two half-pins: the two rooks on the line of the h8 bishop and the two pawns on the line of the h5 rook. A review of White's checking moves reveals the possibility of 1.Qe3+ dxe3 2.d4+ but f4 is unguarded. So will the key be 1.Kg3 or 1.Kf3?} (1. Kg3 $2 {Defence 1:} g4 { Protecting e3 with the bishop on h6} ({Defence 2:} 1... Rxd6 2. Ng4+ {The Rf6 has been lured off the 'f' file, so now White draws the f-pawn off the half-pin line:} fxg4 3. Qf4#) ({Defence 3:} 1... f4+ 2. Qxf4+ Rxf4 {The rook is obliged to capture as the g-pawn has become pinned, but now there is no protection for e6:} 3. Re6#) ({But Black has} 1... Nc3 $1 {, which enables the knight to interpose after 2.Qe3+ with 2...Ne4+ and it's check, so White loses the opportunity to capture on d4 with mate. Now we understand why 1.Kf3! is the key.}) 2. Re6+ {The f-pawn is now pinned, so White plays to draw the Rf6 off the half-pin line, so that the Rg7 becomes pinned as well. 2...} Rxe6 3. Nxg4# {A double pin-mate.}) ({So the key is} 1. Kf3 $1 {Now 1...Nc3 fails to defeat the threat, as 2.Qe3+ Ne4 - not check! - 3.Qxd4#. Defence 1:} g4+ ({ Defence 2:} 1... Rxd6 2. Qf4+ {The g7 rook is now pinned so White plays to have the f5 pawn pinned for another double pin-mate.} gxf4 {(If 2...Kf6 3. Qxd6#)} 3. Ng4#) ({Defence 3:} 1... f4 2. Re6+ {Again decoying the rook away from the protection of f4, to take advantage of the pin on the g5 pawn:} Rxe6 3. Qxf4#) 2. Nxg4+ {Now that the f5 pawn is pinned, White is able to decoy the g7 rook off the half-pin line to leave his brother pinned:} Rxg4 3. Re6# {A superlative mechanism, showing an intricate interaction between the two half-pins. In the play after the try 1.Kg3? the 3 white moves are arranged in the cyclic pattern Defence 1:2.A 3.B; Defence 2:2.B 3.C; Defence 3:2.C 3.A. In the play after the key, the same 3 white moves are shifted into the pattern Defence 1:2.B 3.A; Defence 2:2.C 3.B; Defence 3:2.A 3.C. Little wonder that it is one of the small number of problems that have received a maximum score in the FIDE Albums (selections of problems over 3-year periods, a little like Chess Informant). It deserves at least a half hour's study, reflecting on the composing grandmaster's ambition and ingenuity.}) *

The second problem seems forbidding in length, but succeeds with admirable clarity in showing a modern idea of reciprocal move sequences linked to the traditional Grimshaw and half-pin themes.

[Event "2nd Prize Probleemblad"] [Site "?"] [Date "1987.??.??"] [Round "?"] [White "A.Lobusov & M.Marandjuk"] [Black "Mate in 7"] [Result "*"] [Annotator "Friedgood,David"] [SetUp "1"] [FEN "2rqrb1n/pb1Rp3/1p4pP/Q1ppk1B1/1n1p4/3P1RKB/P4N1P/8 w - - 0 1"] [PlyCount "1"] [EventDate "1987.??.??"] 1. -- {Longer problems like this one can sometimes be easier to solve than shorter ones. This one has a game-like position and the first move is perhaps one which a player might choose without very much thought:} (1. Qb5 {Of course the idea here is not to trap the black queen, but rather the king! 2.Rf6 displayed as the final variation below shows the threat, which leaves Black helpless in the face of multiple mate threats. The only defences possible are to cut off the white queen's protection of the d7 rook by playing a piece to c6.} -- (1... Rc6 2. Ng4+ Ke6 3. Ne3+ Ke5 4. Nc4+ {Prising the d5 pawn off the half-pin line} dxc4 5. Bf4+ Kf6 6. Be3+ {This discovered check has been made possible by the interference on Black's first move by the rook with the b7 bishop.} Ke5 7. Bxd4#) (1... Bc6 2. Bf4+ Kf6 3. Be3+ Ke5 4. Bxd4+ {Have we seen this sequence before? Yes - White's moves 2 to 4 in this variation are the same as White's moves 5 to 7 in the first variation!} cxd4 (4... Kxd4 5. Qc4+ Ke5 6. Qf4#) 5. Ng4+ Ke6 6. Ne3+ Ke5 7. Nc4# {And we've seen this sequence before too - White's moves 5 to 7 in this variation are the same as White's moves 2 to 4 in the first variation! This time, the mating move has been made possible by the bishop's Move 1 interference with the rook, completing the Grimshaw interference pair.}) (1... Nc6 {This variation is non-thematic and also a move short of the full solution length, but it has its points.} 2. Rf7 $1 {A nice quiet move after all the checks in the thematic variations, threatening 3.Bf4# and forcing Black to create a self-block on f7.} Nxf7 3. Bf4+ Kf6 4. Ng4+ Ke6 {or Kf5} 5. Ne3+ Kf6 6. Nxd5#) 2. Rf6 Qxd7 3. Qxd7 {Another rich problem containing a wonderfully ambitious mechanism, with the half-pin on White's fifth rank playing a fundamental role.}) *

The last two diagrams were given for the reader to solve. The first is a straightforward two-mover, with the half-pin already in place. You have to find the key move, which uniquely forces mate on the following move, regardless of what Black does. Having found the key, the real enjoyment is to be derived from Black’s defences to White’s threat and how the first player takes advantage of the weaknesses created by those defences. Almost all the action relates to the half-pinned black pieces on White’s fourth rank.

[Event "1st Prize Hampshire Telegraph & Post"] [Site "?"] [Date "1915.??.??"] [Round "?"] [White "Comins Mansfield"] [Black "Mate in 2"] [Result "*"] [Annotator "Friedgood, David"] [SetUp "1"] [FEN "b3B3/1P3n2/3pp3/BR3p2/kb1n3R/5p2/PPr1r3/K1NQq3 w - - 0 1"] [PlyCount "1"] [EventDate "1915.??.??"] 1. -- {White possesses a powerful battery, comprising the e8 bishop and the b5 rook, pointing directly at the black king. Freeing a5 by moving the bishop on that square will threaten mate by 2.Ra5, with an unanswerable double check. So the key is:} (1. Bc7 $1 {Not 1.Bd8? Nxd8, nor 1.Bb6? which as we will see later, will be needed by the rook.} -- {Now any move of the b4 bishop will defeat the threat by vacating b4. Let's look at the possibilities:} (1... Ba5 2. Rb6# {By moving off the half-pin line the b4 bishop caused the d4 knight to be come pinned, rendering a double check unnecessary. On the other hand, the rook has to keep control of b4, and the only alternative would be 2.Rb3+, but this unpins the c2 rook, which could interpose. Fortunately, the black bishop has blocked the a5 square, so the c7 bishop no longer needs to guard it and the rook can interfere with the bishop in delivering mate! A typically complex variation.}) (1... Ba3 2. b3# {is a simpler self-block variation, which nevertheless also depends on the d4 knight becoming pinned, as well as upon the blocking of a3.}) (1... Bd2 2. Qxc2# {This time the bishop's square-vacating move interferes with the e2 rook, allowing the queen to give mate on c2, again because of the pinned knight.}) (1... Bc3 {(or Bc5)} 2. Rb3# {The fourth and last defence by the b4 bishop results in an interference with the Rc2 rook, enabling the white rook to unpin it in giving mate - yet again relying on the knight being pinned. This is a beautiful echo of the 1...Ba5 defence.}) (1... Nc6 {This move doesn't defend against the threat, because both it as well as the b4 bishop are pinned and unable to capture the rook.} 2. Ra5#) (1... Nxb5 {This drastic defence leaves both knight and bishop pinned, enabling} 2. bxa8=Q#) ({Finally, a non-thematic variation:} 1... Nb3+ 2. axb3#) 2. Ra5# {This is surely one of the greatest traditional half-pin two-movers.}) *

The following three-mover classic is really rather difficult, but is guaranteed to repay the solver’s persistence with some marvellous play. Again, the key uniquely forces mate in 3 moves, but even after you have found it there is a way to go, as White’s responses to Black’s defences are not altogether obvious. This is an anticipatory half-pin and the play turns on the black king’s captures of the d5 pawn.

[Event "1st Prize, Hampshire Telegraph & Post"] [Site "?"] [Date "1920.??.??"] [Round "?"] [White "Gerald F.Anderson"] [Black "Mate in 3"] [Result "*"] [Annotator "Friedgood, David"] [SetUp "1"] [FEN "8/2K2p2/B4P2/1N1P2P1/2k2Pp1/P1pbB3/P1Pq4/3Rrr2 w - - 0 1"] [PlyCount "1"] [EventDate "1920.??.??"] 1. -- {If d5 were guarded an immediate mate would be available using the a6 bishop and b5 knight battery. But the e3 bishop must at all costs be preserved, so as to ensure that d4 is kept under control. Even recognising this, the key is still highly paradoxical - a brilliant move:} (1. Bb6 $3 {This threatens the cool 2.Kc6, followed by the unpreventable 3.Nd6#, comfortably coping with 2...Re6+. But why, to ask the obvious question, is this move preferable to 1. Ba7? It's also astonishing that checks by 1...Qxf4 and 1...Re7 do not defeat the threat. However, in the latter case, we can see that, had White tried 1. Ba7? then 1...Re7+ 2.Kc6 Rxa7 saves the day for Black. Now, any move by the d3 bishop will defend against the threat, by preparing 2...Qxd5+ against 2.Kc6:} Be2 {You now have a two-mover to solve. What's White's key-move? Note: this is a case of anticipatory half-pin:} 2. Kd7 $3 {Another stunner. White's king calmly walks into the very check that Black had prepared, making room for the knight to threaten mate on c7, protecting the d5 square. This takes advantage of the fact that the bishop has interfered with the e1 rook, preventing 2... Re7+. Now if} Qxd5+ (2... Kxd5 3. Nxc3# {gives us the thematic half-pin mate. It is a glorious mirror model mate. [Mirror mate: a mate in which there are no units in the mated king's field. Model mate: a mate in which the squares in the mated king's field are each guarded just once and all the mating side's units are required for the mate, with the permissible exceptions of king and pawns. (In this particular case the king is an important participant in the mate.)]}) 3. Nd6#) (1. Bb6 Qg2 {is the other half of the half-pin, in which Black again attempts to prepare 2...Qxd5+ against the threat of 2.Kc6. This time 2.Kd7 doesn't work, because Black has 2...Bf5+. However, the potential pin on the bishop gives White a different opportunity:} 2. Nd6+ Kxd5 3. Bc4# { Another model mate! This mate would also have been possible had the black bishop moved along the c2 to h7 diagonal, but it would not have been a model, as the white rook would have been unused.}) ({Finally, we note the non-thematic variation} 1. Bb6 Kxd5 2. Bb7+ Ke6 (2... Kc4 3. Nd6#) 3. Nd4# {A sublime work of chess art; surely one of the all-time best problems ever composed.}) *

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Copyright in this article David Friedgood 2012/ChessBase

The British Chess Problem Society (BCPS), founded in 1918, is the world's oldest chess problem society. It exists to promote the knowledge and enjoyment of chess compositions, and membership is open to chess enthusiasts in all countries.

The Society produces two bi-monthly magazines, The Problemist and The Problemist Supplement (the latter catering for beginners), which are issued to all members. Composers from all over the world send their problems and studies to compete in the tourneys run by the society.

The BCPS also organises the annual British Chess Solving Championship, and selects the Great Britain squad for the World Chess Solving Championship. The Society holds an annual residential weekend, with a full programme of solving and composing tourneys and lectures; this event attracts an international participation. Members are also entitled to use the resources of the BCPS library, and the Society book service, which can provide new and second-hand publications.

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