Reproduction of this essay in whole or in part for noncommercial purposes, with attribution and with notice of
copyright, is permitted; reproduction of this essay in whole or in part for commercial purposes, or without attribution,
or without notice of copyright, without the author's express permission, is not permitted.
Chess diagrams appear thanks to Steve Eddins's ChessImager,
available here.
Little Lesson 2: Building Walls
Sometimes, achieving a win or draw requires building a wall that the opponent's king can't cross. The idea of the wall
comes up surprisingly often, especially as games head into endings. One deliberately arranges his
pawns (and his pieces, if there are pieces left) so as to shut out his opponent's king--to prevent his opponent's king
from penetrating his own position, or to prevent his opponent's king from occupying desirable squares. Consider the
following king-and-pawn ending:
If it is White's move, the natural 1 Ke4? loses to 1 ... Ke6 2 Kd3 Kf5 or 2 Kf3 Kd5. (1 Kc3 also loses, to 1 ... Kd5
2 Kd3 [forced, to stop both ... Kc4 and ... Ke4] e4+ 3 Kc3 [again forced, to stop ... Kc4] Ke5 4 Kb3/b2/c2/d2 Kf5 5 Kc3 Kg4
6 Kd4 Kf3, winning the e-pawn and the game; 1 Kd2/c2 lose the same way. 1 Ke2 Kd5 2 Kf3 loses to 2 ... Kc4, as on 3 Ke4
White doesn't queen fast enough.) White has to play 1 e4! White's and Black's pawn structures then form walls that
keep the opposing kings out, and the game is drawn. (I'll note that the same White losses after 1 Ke4? occur if the
Black king starts off on d6/d7/e7/f7/f6--anywhere it can reply to 1 Ke4? with 1 ... Ke6. But if the Black king were on
e6 in the diagram, then White could play 1 Ke4; both sides would queen, in that case.)
In the following
positions, White draws by preventing Black's king ingress to his position:
In the left-hand position, Black's king cannot penetrate White's position without advancing his h-pawn. White's king
can shuttle back and forth, using the squares g3, h3, and h4; Black's extra pawn does him no good. As soon as Black
moves ... h4, White captures the pawn:
1 Kh4 Kg6 2 Kh3 h4 3 Kxh4 Kh6 4 Kh3 Kh5 5 Kg3 Kg6 6 Kh4 Kh6 7 Kh3, etc. Once the pawn is captured, the kings have
h3/h6 and g3/g6 to shuttle back and forth on, White's king preventing Black's king entry to g4 and Black's king
preventing White's king entry to g5.
In the right-hand position, the situation is a little more dangerous for White. Black's king has the g5 square
through which to penetrate into White's position. If Black's king were on h6 instead of h7, and if it were
Black to move, Black would win by moving 1 ... Kg5; White's king could not both guard against the h-pawn and
cover the White e-pawn. White's e-pawn and f-pawn would fall, and Black's e-pawn and f-pawn would win.
But Black's king isn't on h6; it's on h7. The position is drawn no matter who moves first. Curiously, Black can't move
his king to h6 without losing his h-pawn, in which case the game is drawn, since after that the Black king blocks the
White king's entry to g6 by playing ... Kh6/h7/g7 and the White king blocks the Black king's entry to g5 (or, really, to
f4) by playing Kh5/h4/g4 (once the h-pawn is gone, White can permit Black to place his king on g5, as long as White then
plays Kg3--but, once the h-pawn is gone, White cannot permit the kings to occupy g5 and g3 with White to move, for then
Black will win by outflanking White.) E.g., 1 ... Kh6 2 Kh4 Kh7 3 Kxh5 Kg7
4 Kh4 Kh6 5 Kg4 Kh7 6 Kh5 Kg7 7 Kh4 Kh6, Draw.
The position should be drawn no matter what Black does, though, so giving up his h-pawn really shouldn't matter. However,
White
could lose, by playing 1 Kh4 in the diagrammed position. Black then plays 1 ... Kh6; White's king has to retreat,
Black's king gains entry to g5, and Black wins. White must, therefore, not play Kh4 until Black plays ... Kh6;
until then, White must simply play Kg3/h3, waiting for Black's ... Kh6.
Position after 60 ... Kg3
Position after 63 Nb3
Position after 71 Kg3
The positions above are from one of my tournament games (Johnson-Eric Brandt, 7 OCT 2006, WCCC First Saturday of the Month
Quads). In a sudden-death time control, I didn't remember a systematic way of checkmating with bishop and
knight, but I knew this much: Walls are involved, and White's goal is to checkmate Black's king in a light-squared
corner. Black's king has already been herded from h8 to g3. But it looks as though the Black monarch will flee to the
dark-squared corner a1! Play continued 61 Kg5 Kf3 62 Nd4+ Ke3 63 Nb3! (See middle diagram.)
Now White's King, Knight, and Bishop cooperate to form an h4-g4-f4-e4-d4-d3-d2-c2-c1 wall. The Black king can't escape to a1
after all. Play continued 63 ... Ke2 64 Kf4 Kd1 65 Ke3 Ke1 66 Bg4 (cutting off d1 and forcing Black's king to f1) Kf1
67 Bf3 (cutting off g2) Ke1 68 Nc1 Kf1 69 Nd3 (cutting off e1 and forcing Black's king to g1) Kg1 70 Kf4 Kf1 71 Kg3
(See rightmost diagram.)
White's pieces form another wall, this time along the e1-e2-f2-g2-h2 squares, restricting Black's king to f1, g1, and h1.
Soon Black will be checkmated. Play continued 71 ... Kg1 72 Be2 (cutting off f1) Kh1 73 Nf4 Kg1 74 Nh3+, and Black
resigned, in view of 74 ... Kh1 75 Bf3 mate.
Position after 29 ... Ng7
Position after 35 ... Nc7
Position after 39 ... Kf6
These positions are from another of my tournament games (Frank Jackson-Johnson, 1 MAR 2008, WCCC First Saturday of the
Month
Quads). I had lost a pawn for nothing, and after 29 ... Ng7 (see leftmost diagram) I was fighting for a draw. White had
to be happy, having an extra pawn
and a bishop for knight in an endgame with pawns on both sides of the board (bishops are generally better than knights
in such endings, because they can quickly get from one side to the other and can control squares on both sides of the
board simultaneously, an advantage that vanishes once pawns are only left on one side of the board [at which time the
knight's ability to control squares of either color may be more valuable than the bishop's greater mobility]). The
bishop's mobility is, however, inhibited by the White pawns on c4 and d5. I don't
assert that the next few moves were the best possible for either side, but play continued 30 b4 b6 31 Kd2 Kf7 32 Kc3 Kf6
33 bxc5 bxc5 34 Kb3 Ne8! 35 Ka4 Nc7 (See middle diagram)
Black's a-pawn and knight form a wall of squares a6-b6-b5 that the White king can't cross. Since neither pawn nor knight
is on a dark square, neither can be chased away by White's bishop, so White will make no headway on the queenside. Play
continued 36 g4 Kf7 37 h4 h6 38 h5 gxh5 39 gxh5 Kf6 (See rightmost diagram)
And now the game is drawn! If White's king tries to break through on the queenside, Black will simply play his king to
e7/f7/g7/f6, leaving the a6-pawn and knight to keep the White king out with the a6-b6-b5 wall; if White's king tries to
break through on the kingside, Black will keep his king on f6, so that his d-pawn, king, and h-pawn form an e5-f5-g5
wall, while moving his knight on the c7/a6/a8/e8 squares. Since White's bishop can only control two of the three squares
a6, a8, and e8 simultaneously (on b7, the bishop would control a6 and a8 but not e8; on c6, it would control a8 and e8 but
not a6; on b5, it would control a6 and e8 but not a8), Black will always have at least one light-colored square to move
his knight to from c7, so
the f6-king can't be forced to move and allow the White king to break through on the kingside. And since Black's pawns
are all on dark squares, and since the c7-knight sits on a dark square, the light-square bishop has no targets.
White spent another twenty-eight moves convincing himself this was a draw. And why not? He's up a pawn and has a
bishop for a knight in an endgame with pawns on both sides of the board! But the two walls stop him from making
any progress, and the game is completely drawn. The rest of the moves, in case the reader needs any more convincing that
the position is drawn (although at this point it should be clear), were 40 Bg6 Kg7 41 Ka5 Kf6 42 Ka4 Kg7 43 Kb3 Kf6
44 Kc3 Na8 45 Bc2 Nc7 46 Kd2 Na8 47 Ke3 Nc7 48 Ke4 Na8 49 Ba4 Nc7 50 Bd7 Na8 51 Kd3 Nc7 52 Kc3 Ne8 53 Kb3 Nc7 54 Ka4
Ke7 55 Bc8 Kf6 56 Ka5 Ke7 57 Ka4 Kf6 58 Kb3 Ke7 59 Kc3 Kf6 60 Kd3 Na8 61 Ke4 Nc7 62 Bd7 Na8 63 Bb5 Nc7 64 a4 Na8 65
a5 Nc7 66 Bc6 ... Draw agreed.
The idea of a wall also arises in an analysis variation from Hermans-Johnson (see
here):
After 32 ... bxc5
After 33 ... a4 (analysis)
The actual game position occurred as in the leftmost diagram. White then played 33 bxc5+. But had he played 33 b5, he
would have set a trap for Black: If Black doesn't play ... a4, White will play a4 himself, and that will hold the
draw.
33 b5, however, can be answered by 33 ... a4 (see rightmost diagram). Then the Black pawns form a b3-b4-c4-d4-e4 wall,
preventing the White king from doing anything useful. In particular, the White king cannot defend the White b-pawn. The
White king remains passive and ineffectual, while the Black king can pick off the b-pawn at its leisure. White's
crippled kingside pawn majority is useless to him, and the two Black central pawns easily win.