Ending 9
The separated knight becomes the target, corner trap patterns that are theoretically lost, the knight's dumb square, and a practical example from elite chess showing how difficult the defence really is.
Once the knight becomes separated from its king, the stronger side's main objective is to trap it. The trapping process usually involves restricting the knight's mobility, taking away escape squares, using pins and double attacks, and bringing the king closer.
Position 1.20 · Rook vs Knight: Separated Knight · Black to move
FEN: 8/8/8/3N4/8/5k2/2r5/4K3 b - - 0 4
The white knight on d5 has moved away from the king on e1 and is very likely to be lost. The black rook on c2 and king on f3 are well placed to begin the hunt.
Main line
The rook gradually removes every escape square until the king can capture the knight.
Variation — 5.Nf6
Variation — 6.Nd5
Variation — 7.Nd6
Continuation from the previous position. There is one case where a temporary separation is acceptable.
Main line
The king immediately returns beside the knight. This is the only acceptable temporary separation.
Everything changes once both defending pieces are trapped near the corner. Mobility disappears, and the knight is normally lost.
There is no need for lengthy calculation. This configuration is theoretically lost.
Position 1.21 · Corner trap pattern · White to move
FEN: 8/8/8/8/8/6k1/r7/6NK w - - 0 1
The white knight on g1 and king on h1 are trapped near the corner. The black rook on a2 and king on g3 have full control. White loses the knight immediately.
Both defending pieces are trapped in the corner, so the knight is lost.
Position 1.22 · Both pieces in the corner · White to move
FEN: 8/8/8/8/8/6k1/r7/6KN w - - 0 1
With the king on g1 and the knight on h1, both pieces are trapped. The rook easily wins once both defending pieces have no room to manoeuvre.
Even with the knight on g2, it is lost because both pieces are trapped. This is the first appearance of the knight's dumb square.
Position 1.23 · The knight's dumb square · White to move
FEN: r7/8/8/8/8/6k1/6N1/7K w - - 0 1
The knight on g2 is not on the edge itself, but it is still trapped because of the surrounding geometry. The king on h1 has no escape, and the rook on a8 controls everything.
The two defensive rules to remember from this section:
Bacrot promoted to a knight, reaching what is generally considered a theoretical draw. However, the knight is dangerously close to its dumb square, making defence much harder than expected.
Position 1.24 · Kamsky vs Bacrot, Sofia 2006 · White to move
FEN: 8/8/8/8/8/5K2/7R/4nk2 w - - 0 1 · Bacrot has just promoted to a knight.
The position looks like a standard draw, but the knight on e1 is dangerously close to the dumb square g2. Defence requires extreme precision.
Main game — forced phase
Up to this point the moves are essentially forced. Now Black faces a critical decision.
Game continuation
This is the losing move.
Correct defence
This returns to a drawable setup.
An amazing zugzwang position after 11.Rh7. Black is to move and has no good option.
Position 1.25 · Zugzwang after 11.Rh7 · Black to move
FEN: 8/7R/8/8/8/8/4K1n1/6k1 b - - 0 11
The knight on g2 — the dumb square — has almost no safe moves. The king on g1 is boxed in. Black is in complete zugzwang.
Principal variation
This misses the strongest continuation.
Better
Game continuation
15...Nd7! would have drawn.
Remaining moves