The first problem is a straightforward one – the half-pin is ready for action in the start position on the diagonal c1 to f4.
The second problem, a fourmover, also has the half-pin set up in the diagram, but the idea of the composers is not so much to exploit the pinning of the pieces as to decoy both of them off the half-pin line to be able to control a square in the black king’s field.
The last two diagrams are for the reader to solve. In each case, you have to find the unique key move, which forces mate on White’s third move. For each black defence to the threat you have to find the continuation for White, Black’s response(s) and finally the mate.
White to play and mate in three
In the above problem, the half-pin has yet to come into being. It’s quite easy to find how Black can be induced to inadvertently create the half-pin by an appropriate key and threat. Then the question is how to exploit the half-pin.
White to play and mate in three
This problem has a solution in which the half-pin is activated before it exists! You should be able to see from the diagram how the half-pin might come about, but the sequence of moves might surprise you.
{The pleasing, if slightly obvious key is} 1. Qd8 {with the threat of 2.d4+
and mate next move. If} Bxd8 ({The thematic variations feature captures of
the
pawn on e3, thus creating a halfpin with the capturing piece and the knight
on
e4 on the line of the rook on e2.} 1... Bxe3 2. d4+ {White's strategy is to
decoy the piece on e3 away, so as to leave the knight pinned.} Bxd4 3. Qxg5#)
(
1... Rbxe3 2. Nd3+ Rxd3 3. Qf6# {Note that this mate is possible as the rook,
in capturing on e3, opened the line of the bishop on a2 to take over
protection of d5.}) (1... Rhxe3 2. Nf3+ Rxf3 3. Qd6#) 2. d4+ Kd5 3. Bxb3#
{An
elegant problem, but the half-pin is incomplete (there is no variation where
the knight moves leaving the piece on e3 pinned) and the 1...Bxe3 variation
is
met by the first move of the threat.} *
[Event "1st Pl League of Macedonian Problemists"]
[Site "?"]
[Date "2006.??.??"]
[Round "?"]
[White "Aaron Hirschenson"]
[Black "Mate in 3"]
[Result "*"]
[Annotator "David Friedgood"]
[SetUp "1"]
[FEN "1B1q2B1/2r5/3r1p2/N4kPp/1p3N1P/4pK2/6PP/Q5b1 w - - 0 1"]
[PlyCount "5"]
{The key is very easy - you only have to spot the idle pawn on h2!} 1. h3
{
threatening 2.g4+} {Black's two defences create a flight square for the king
on e5:} Rc3 (1... Rd4 2. Be6+ {Avoiding 2.Bh7+? Rxh7} Ke5 {The king arrives
on
the half-pin line! This odd situation, where the king does not start off on
the half-pin line, has led to the term 'anticipatory half-pin'} 3. Nc4#) 2.
Bh7+ {Avoiding 2.Be6+? Rxe6} Ke5 3. Nc6# {A clear illustration of the
anticipatory half-pin. Both mates are double pin-mates. The too simple key
is
a pity.} *
Any queries or constructive comments can be addressed to the author at david.friedgood@gmail.com.
Copyright in this article David Friedgood 2012/ChessBase
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