A Guided Tour of Chess
by Tim Krabbe

The Mother of All Forks
Band 5: practical themes.

From the everyday themes in this band - like the breakthrough;
square- and line-vacating; the Zwischenzug; forks and skewers
- I chose what is perhaps the most elementary of all tactics, the
fork. One reason is that recently, in the electronic newsletter of
a chess club in Amsterdam, the fork was hotly discussed. This
started when one contributor, commenting on his Qd6, which
attacked two Rooks on b8 and f4, innocently called it a fork.

In the next issue, somebody else protested that this wasn't a fork
at all because the teeth of a real fork do not point away from
each other. When the discussion really got going, it turned out
there were vastly different views about what a fork really is.
Some thought both teeth of a fork must point forward; that only
Knight and Pawn can fork; that the King can do it too, but not
the Rook, Bishop or Queen; that a fork must be symmetrical;
that empty squares can be forked too; that the attacker must be
of less value than the attacked, 'because a fork cannot prod
anything smaller than its teeth.' There was also somebody who
thought a fork is only a fork when the forking piece moves to
the square where it forks.

That's something I want to refute at once. (See Diagram) 

White: Kg2, Rd4, Rf4, Bd3; pawns - b5, c2, g5, h4
Black: Ke5, Re3, Rh8, Bc8; pawns - a7, d5, f5, g6

Black to play; NN - Mannheimer, Frankfurt am Main 1921.
With 1...Re4!, Black activated the fork that Ke5 already gave.
White resigned; he loses a piece.

Just like the readers of that newsletter, chess encyclopedias
disagree about the fork. They all say it is a double attack in
different directions by one piece or a pawn, but sometimes that
is the whole definition (and in that case empty squares count
too, making any move, except h2-h4 and Ba1-h8, a fork) and
sometimes again, it is only the pawn which can fork.

In my own definition that I use here, not so much to be pedantic
as to limit the subject, I'm adding a clause that I saw nowhere
else: the double or multiple attack must not be aimed at the
King; in that case it is a 'Family Check'.

The basic fork, agreed, is a pawn prodding two pieces; one of
the first tactics a beginner encounters. Often a gross blunder
allows one, and one soon learns the part it plays in standard
pseudo sacrifices like 1.e4 e5 2.Nf3 Nc6 3.Nc3 Bc5 4.Nxe5
Nxe5 5.d4

An elementary but surprising serial fork is seen in this game:

Grigoriev - Panikovsky, Kurgan 1972: 1.e4 c5 2.Nc3 Nc6 3.g3
g6 4.Bg2 Bg7 5.d3 d6 6.f4 Nh6 7.Nf3 f5 8.O-O O-O 9.h3 Nf7
10.Be3 Nd4 11.Qd2 Rb8 12.Bf2 fxe4 13.Nxd4 A
Zwischenzug. (See Diagram)

But Black had the Zwischen-Zwischenzug 13...e3! and after Q
or Bxe3 there would follow something resembling a multiple
jump in draughts; cxd4 and dxe3 or dxc3. After 14.Ne6 exf2+,
White resigned.

Another sort of serial fork, by Tal. (See Diagram) 

White: Kg1, Qd1, Rc1, Re1, Bg2, Na3, Ne4; pawns - a2, b2,
c4, f2, g3, h4
Black: Kg8, Qd8, Ra8, Re8, Bf5, Nb4, Ng6; pawns - a4, b7, d3,
f7, g7, h6

Black to play. In Kochiev - Tal, Moscow 1981, Black played
25...d2, forking the Rooks, but also vacating d3 where a second
fork of those same Rooks will follow: 26.Qxd2 Nd3 winning
the exchange and a little later the game.

A funny case of a fork met by a counterfork: (See Diagram) 

White: Kg1, Qc2, Ra1, Re1, Bc1, Bg2, Nd2, Nf3; pawns - a2,
c4, d4, e4, f2, g3, h3
Black: Kg8, Qc7, Rb8, Rf8, Ba6, Be7, Nb6, Nf6; pawns - a5,
c6, d6, e5, f7, g7, h7

White to play. In Tretyakov - Zhuravlev, Riga 1978, White saw
a fork that wins a pawn: 1.dxe5 dxe5 2.Qc3 But he didn't see
the counterfork: 2...Bb4 3.Qxe5 Qxe5 4.Nxe5 Bc3 which wins
a piece.

An unusual fork happened in Razuvajev - Mestrovic, Keszthely
1981 (See Diagram)

White: Kg1, Ra8, Rc8, Ng5; pawns - f2, g2, h3
Black: Kg8, Rf8, Rf6, Nd3; pawns - e5, g7, h6

White to move. With 38.Nh7!, he won the exchange (38...Rxc8
39.Nxf6+) and soon the game.

There are several standard middlegame traps which are based
on forks - here is one which has made many victims over the
years. It was first seen in Norman - Vidmar, Hastings 1925:
1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.Nf3 O-O 5.e4 d6 6.Bd3 Bg4
7.h3 Bxf3 8.Qxf3 Nc6 9.Be3 Nd7 10.Ne2? (See Diagram) 

And now 10...Nce5 won a pawn, and destroyed White's
position. After 11.dxe5 Nxe5 12.Qg3 Nxd3+ 13.Kf1 c5 14.h4
Qd7 15.h5 Qe6 16.Rh4 Qxc4 17.hxg6 fxg6 18.Qh3 Nxf2
19.Bxf2 Bd4 White resigned. 

This exact position has occurred more often - I found 12 games
with it in my database, the last one from 1998. In a slightly
different form, in another opening, it has also happened 13
times - at surprisingly high levels. The debut of that fork was:

Ljubojevic - Timman, Tilburg 1978: 1.e4 d6 2.d4 Nf6 3.Nc3
g6 4.f4 Bg7 5.Nf3 c5 6.dxc5 Qa5 7.Bd3 Qxc5 8.Qe2 O-O
9.Be3 Qa5 10.O-O Bg4 11.Qf2 Bxf3 12.Qxf3 Nc6 13.Ne2
Nd7 14.c3 (See Diagram)

14...Nde5 15.fxe5 Nxe5 16.Qh3 Nxd3 17.Qd7 Qa6 18.Qxe7
Rae8 19.Qh4 d5 20.Ng3 f5 21.e5 f4 22.Bxf4 Qb6+ 23.Kh1
Nf2+ 24.Rxf2 Qxf2 25.Rf1 Qxb2 26.Qg5 and White resigned.

You'd think this would have been a good warning, but with a
minor modification (pawn h2 being at h3 because of the
intermediate 11.h3 Bxf3 12.Qxf3 etc.) this has also happened
in, among others:
Zapata - Chernin, Cienfiegos 1981
Hbner - Korchnoi, Skelleftea 1989
Korneev - Van Wely, Krumbach 1991

All together, I found 34 games where this Ne5-fork was
possible. It was missed 6 times - never in master games, except
for this one:

Gligoric - Pirc, Bad Pyrmont 1951: 1.e4 c5 2.Nf3 d6 3.d4
cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.f4 Qc7 7.Bd3 Bg4 8.Nf3 Nc6
9.h3 Bxf3 10.Qxf3 e6 11.O-O Be7 12.Be3 O-O 13.Ne2 Nd7
14.c3 (See Diagram)

14...Rad8 c3 looks like a trap, but I don't see why Ne5 couldn't
have been played: 15.fxe5 Nxe5 16.Qg3 Nxd3 17.Bh6 Qc5+
followed by Qe5, and Black seems to be better. In reality,
White won after: 15.Rad1 d5 16.e5 Bc5 17.Nd4 Bxd4 18.cxd4
f5 19.g4 g6 20.gxf5 gxf5 21.Kh1 Kh8 22.Rg1 Rg8 23.Qh5
Rde8 24.Qh6 Nd8 25.Bf2 Nf8 26.Bh4 Rg6 27.Bf6+ Kg8
28.h4 and Black resigned.

For forks aimed purely at winning material there is nothing like
this: (See Diagram)

White: Kg2, Nh3
Black: Kd2, Nf1, Nh5; pawn - e2

White to play and draw; A. Herbstmann & L. Kubbel, 1st
Prize, Troitzky-Tourney, 1937. White cannot stop the pawn
by ordinary means; moves are dictated by Family Checks on f3;
knight-stalemates; pinning stalemates by a new Queen on e1;
and by the knowledge that the endgame of three Knights against
one Knight is won - something first demonstrated by Troitzky.
1.Ng1 Ne3+ (Nf4+ 2.Kh1 e1N 3.Nf3+ Nxf3 stalemate) 2.Kh3
Nf4+ (2...e1N 3.Nf3+ Nxf3 with a beautiful three-Knight
stalemate) 3.Kh2 Ng4+ (Not 3...e1N 4.Nf3+ Nxf3+ 5.Kg3 and
White forks two Knights; or again 3...Nf1+ 4.Kh1 e1N 5.Nf3+
Nxf3 stalemate) 4.Kh1 Nf2+ (Again both promotions are, or
lead to stalemate) 5.Kh2 e1N Finally. No stalemate seems in
sight. 6.Nf3+ Nxf3+ 7.Kg3 (See Diagram)

White: Kg3
Black: Kd2, Nf4, Nf3, Nf2

A fork of three Knights - Black needs them all to win. So he
must play 7...Ke3, but that is stalemate once again. Witty and
beautiful, this belongs to my 10 favorite endgame studies.

A unique sort of fork is seen in this amazing study. White to
play and draw; F. Simkhovitch, 1st Prize Turkmenskaya
Iskra, 1940. (See Diagram)

White: Kh2, Be4; pawns - c3, f7, g2, g3, g6
Black: Ke7, Rd4, Rg4

After 1.cxd4 Rxe4 Black wins, and after random Bishop moves,
the Rd4 just moves away, and again Black wins. 1.Bf5!
however, restricts Black. 1...Rde4 then fails to 2.Kh3, and
1...Rg5 to 2.g7 Kxf7 3.g8Q+ Kxg8 (the Rg5 must keep
attacking the Bf5) 4.Be6+, and White has time for cxd4.
Therefore, Black must choose between 1...Rc4 and Ra4. But
wherever the black Rook goes, there follows a sort of perpetual
fork, e.g. 1...Rc4 2.Be6 Ra4 3.Bd7 Rge4 4.Bc6 Rac4 5.Bd5
Ra4 6.Bc6 Rec4 7.Bb5 Rg4 8.Bd7 Rae4 9.Bf5 and so on,
always keeping both Rooks under attack and never capturing
one. For each pair of squares that the Rooks have, there is a
corresponding square for the Bishop. And if Black makes a
waiting move, 9...Kf8, White makes a waiting move too:
10.Kh3! and the double attack continues. e.g. 10...Kg7 11.Kh2!
Rc4 12.Be6 etc.

That is not all in this ingenious study. One might wonder why
1.Bf3 does not work. The same perpetual fork seems possible
from the other side; 1...Rc4 2.Be2 Ra4 3.Bd1 Rge4 4.Bc2 Rec4
5.Bb3 etc. In that case however, Black exploits a hidden
weakness in White's position: after 1.Bf3? he plays 1...Ra4 (he
can also shuffle around for a bit first) 2.Bd1 Kf8! and now it
turns out that White's waiting move has a surprise drawback:
3.Kh3 Ra1! 4.Bxg4 Rh1 mate.

An appealing sort of fork, which is indirectly aimed at mate, is
hidden (not so well, you'd think) in the following position: (See
Diagram)

White: Kh1, Qa6, Rf6, Bf7; pawns - g2, h2
Black: Kh8, Qe4, Rd8; pawns - e5, g7, h7

Black to play. My source (from 1973) unfortunately does not
give the names of the players, and just says that White and
Black were two 'Swedish amateurs'. After 1...Qb7? 2.Qf1
White won, but with 1...Qc6!, Black could have turned the
tables.

This sort of fork, where two line-pieces are forked on one line,
is often seen in connection to the back rank mate, but of course
it can be motivated differently. (See Diagram)

White: Kh1, Qc7, Rd1, Bb2; pawns - a3, b4, c5, f3, g4, h2
Black: Kh4, Qc2, Rg2; pawns - a7, g5, h7

White to play. Csulits - Bade, GDR 1972. White is a piece and
three pawns up, but the threatening black King makes his
position very dangerous. And in fact, he lost after 37.Qd6? h5!
38.Be5? (38.Rd2 still draws) 38...Kh3! 39.c6 Rxh2+ and
White resigned; it is mate next move. In the diagram, 37.Rc1 is
winning, but much more forceful would have been 37.Rd2! -
Black would have had to resign immediately; his forked Queen
and Rook are overloaded.

And a clear, be it somewhat schematic example from an
endgame study: (See Diagram)

White: Ka2, Re7; pawns - b7, d7, f7
Black: Kd8, Rb1, Rf1; pawns - a5, a4, a3

White to play and win; V. Kalandadze, 1965. Direct attempts
at promotion only lead to winning a Rook and losing all the
pawns, and therefore to a draw. With the obvious 1.Re1 White
forks the Rooks which are each tied to one white pawn, and that
seems to be it: Black takes pawn; White takes Rook and wins.
But Black has a temporary escape: 1...Rb2+ 2.Kxa3 Rff2
Which only leads to the next fork: 3.Re2! And so on: 3...Rb3+
4.Kxa4 Rff3 5.Re3! Rb4+ 6.Kxa5 Rff4 7.Re4 and only the
fourth fork finally does it.

A fork may also be aimed directly at mate, as in this early
elegant problem by the great American wizard: (See Diagram)

White: Kh1, Qc4, Nf8; pawn - f7
Black: Kh8, Ba1; pawns - g7, g4, h7

White mates in 3; Sam Loyd, Leipziger Illustrirte Zeitung
1869. 1.Qf1! and now the Queen can always attack h7 while
providing a diagonal QxB mate against the defense g6. After
any Bishop move, the Queen will fork h7 and the Bishop. e.g.
Bb2 2.Qb1 or Bf6 2.Qf5. And after 1...g3, there is another mate
with 2.Ng6+

Another well-known multiple fork by a great American
composer: (See Diagram)

White: Kh2, Qf3, Rb7, Bc7, Ng1; pawns - a2, b6, c2, c6, g2
Black: Ka8, Ra5, Re8; pawn - h5

White mates in 3, W.A. Shinkman, Detroit Free Press 1882.
After the waiting move 1.Kh1! the black Rooks are moving
targets which White can always hit both at once, e.g. 1...Ra4
2.Qe4 or 1...Rh8 2.Qc3, or 1...h4 2.Qh5. In eight variations, it is
mate on the third move by the Queen taking one of the Rooks
or, if she is taken herself, by Ra7 or Rb8.

It is no coincidence that we already encountered Leonid Kubbel
here: the fork, in all its simplicity, was one of his favorite
themes. He also used it in problems; it is not generally known
that in that discipline too, he was one of the greats. (See
Diagram)

White: Kh8, Qg8, Rf5, Bd8, Nb3; pawns - b6, c3, e3, g2
Black: Kd6, Qb1, Ra4, Rh4, Bc5, Bc8, Na6; pawns - c6, d7, d4,
d3, e7, f6, h5

White mates in 4. L. Kubbel, Shakhmaty 1937. Not an
elegant position, but these forks come at a price - which is
worth it. The hero is the inconspicious Nb3, which forks its
way to three mating squares. After the key move 1.c4 (most
other tries fail to Qxb3), 2.Rd5+ and mate next move is
threatened. Black can meet this threat in different ways, leading
to different Knight's forks and a cyclical permutation of mates:
1...Rxc4 2.e4! Rxe4 3.Nd2 and 4.Nxe4 or Nxc4 mate
            2...Bb7 3.Na5! and 4.Nxc4 or Nxb7 mate
1...Bb7 2.Qf7 Re4 3.Nxc5 and 4.Nxb7 or Nxe4 mate

Many years later, two joint Russian composers showed a vastly
improved rendering of this beautiful idea. The position was
lighter, more elegant, there was more unity (the threat was a
mating fork now, too), and they upped the number of variations
from three to five, doubling the number of mating squares to
six. (See Diagram)

White: Kb4, Rc2, Re6, Bb1, Bh8, Nb2, Nf6; pawns - b3, b5, c6,
f3
Black: Kd4, Rf2, Rg6, Ba4; pawns - c7, d5, e5, e3, f5, h4

White mates in 4. A. Virtmanis & V. Chekarkov, 2nd Prize,
Shakhmaty v SSSR 1979. It might be obvious (after a few
hours) that White must first block the Pe3, to rob Black of a
possible flight square. After 1.Re2! there is already the
beautifully thematic threat: 2.Ng4 Rxe6 3.Nxe3 and Nc2 or
Nxf5 mate.
Black now has four defences, which all lead to a new Knight's
fork:
1...Rxe2 2.Nh5! Rxe6 3.Nf4 and Nxe2 or Nxe6 mate
1...Rxf3 2.Nh7! Rxe6 3.Ng5 and Nxf3 or Nxe6 mate
1...Bxb3 2.Nd7! Rxe6 3.Nc5 and Nxb3 or Nxe6 mate
1...Bxb5 2.Ne8! Rxe6 3.Nxc7 and Nxb5 or Nxe6 mate

A simultaneous double fork, both parts satisfying all conditions,
is the core of a wellknown study, worthy to conclude this
survey: (See Diagram)

White: Kg8, Bc8, Nd6; pawns - f4, g3, h4
Black: Kh5, Rf1, Rh2; pawns - f6, g5, h6

White to play and win. G. Kasparian, Shakhmaty 1935.
1.Ne8 Threatening Ng7+ and Bf5 mate 1...Kg6 2.h5+ Rxh5
3.f5+ Rxf5 4.g4 Rc5 Or any other move by that Rook. 5.Bf5+
Rxf5 6.Ng7 and the Rooks on f5 and h5 are doubly doubly
attacked; mate next move. This is certainly the Mother of All
Forks. The fantastic final position is seen one move earlier after
1...Rxf4 2.Ng7+ Kg6 3.h5+ Rxh5 4.Bf5+ Rxf5 5.g4 (See
Diagram):

White: Kg8, Ng7; pawn - g4
Black: Kg6, Rf5, Rh5; pawns - f6, g5, h6