Problem chess: The Self-block

2/21/2012 – It is one of the building blocks of the chess problem: Black (the defending side) is forced to block flight squares in the king's field and thus enable mate. Our problem expert David Friedgood demonstrates this with a remarkable problem with a record of eight self-blocks – arguably the most perfect two-mover ever composed. There are also two self-block problems for you to solve.

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David Friedgood: The Self-block

In this article we go back to basics by looking at one of the main building blocks (no pun intended!) of the chess problem: the self-block. I use this term specifically to mean the blocking of squares in the king’s field to enable mate. A simple example is my own first problem, which I quoted in my first article. Please review this little problem for background.

The following classic problem is a symphony on the theme of self-blocks.

Sir Jeremy Morse, in his book Chess Problems: Tasks and Records (Faber and Faber 1995) says: "The overall record of eight self-blocks was first achieved [in this problem], arguably the most perfect two-mover ever composed." As he points out, there is a ninth self-block in the set play, after the Pc6 is captured. Without any doubt, a classic to be committed to memory!

Mate in two moves

This problem is for you to solve. It shows three self-blocks on a single flight square [a flight square, or flight, is a square to which the black king can move], which is evident in the diagram. You have to find the unique key move by which White forces mate on move two; the self-blocking and any other defences to the threat contained in the key; and also the mates that counter those defences. These mates constitute a charming counterpoint to the thematic defences, which I am sure you will easily spot.

Longer problems can make use of self-blocks to provide interesting Depth effects, as our next example demonstrates. By Depth I mean that the effect or point of a move is seen not immediately, but later in the play. The self-blocks shown in this problem are prospective, in that they occur on Black’s first move, but their blocking effects are seen only on White’s fourth (mating) move.

Mikhail Marandyuk
1st Prize Shavyrin-50 Jubilee Ty, 2003

Mate in four

This four-mover came up in the 2009 British Solving Championship. Of course, Mate in four can be horribly difficult, but on this occasion the key move was obvious to an experienced solver. You just have to ask yourself ‘What on earth is that pawn doing on h2, especially since g3 is already guarded by the Nh5?’

So we try 1.h3! This is confirmed by finding the threat, which depends upon g4 being guarded: 2.Be6+ Ke4 3.Bxc4+ Kf3 4.Bd5#. Now the defences need to be found and then the continuations to each, including any sub-variations – solving can be hard work!

The first defence is 1...Nf3 and we then have to discover 2.Re3! threatening 3.Be6# (not so easy to find, as it sacrifices the rook - in a moremover the continuations can easily be harder than the key!) 2...Nxe3 3.Be6+ Ke4 4.Nc5#. The black knights turn out to be blocking two squares necessary for this position to be mate! An alternative in this line 2...Ne5 is a non-thematic sub-variation: 3.Bxe5 Nxe3 (3...c3 4.Be6#) 4.Nf6#.

The next thematic variation is easier for the solver, as it is very likely to parallel the first: 1...Nd3 2.Bc3! This threatens 3.Nf6# now that the bishop has passed over the critical square e5. 2...bxc3 3.Nf6+ Kd4 4.Re4#. Now the Pc3 and the Nd3 turn out to be the two necessary self-blocks.

The non-thematic variations still have to be found (this is where solvers lose marks!):

  • 1...Rd2 2.Re5+ Kd4 3.Rxe1+ Kd5 (3...Kd3 4.Nxb4#) 4.Be6#;
  • 1...Re2 2.Rxe2 Ne3 3.Rxe3 any 4.Be6#.

This is a three-mover for you to solve. You have to find a key that threatens to force mate on the third move and which provokes the defences, three of which are prospective self-blocks. A clue is that in the threat and all variations White checks on the second move – a quick one-two. The solution will appear next week.

Mate in three

A challenge to readers

How often do you think an active self-block occurs in chess games? [By active is meant that the self-blocking move occurs during the play, unlike the Pg2 in my first problem – see above – which is a passive self-block in the 1...Kxf2 variation.] Can you produce at least one convincing example from actual play, in which, during a mating attack, the defender was forced to block one or more squares, which was/were subsequently necessary for mate to be forced?

The only restriction is that the game must exist in any one of the Chessbase Database products. Please send PGNs to

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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