The Principle of Two Weaknesses
One target can be defended. Two, on opposite wings, cannot.
The principle of two weaknesses says that a single weakness is rarely enough to win: the defender parks a piece next to it and holds. Winning means creating a second weakness, as far from the first as possible, so that the defense has to be in two places at once and cannot.
Play this ending (free)Why one weakness is not enough
Give the defender exactly one problem and he will solve it. A backward pawn gets a king planted in front of it; a passed pawn gets blockaded; a weak square gets covered. Defense is easy when it is local. The attacker can pile up, and the defender simply keeps enough force on the spot, and the game peters out.
The fix is not more pressure on the same target. It is a second target. The defender's pieces are already committed to weakness number one, so a new problem on the other side of the board arrives at a defense that is short-handed by exactly one piece. Every tempo he spends running back and forth is a tempo you spend improving.
That is the whole content of the principle, and it explains a strange practical fact: in many won endgames, the winning move is not an attack at all. It is a pawn advance on the quiet wing, or a king walk toward a target nobody was looking at.
Distance is the weapon
The two weaknesses must be far apart. Two targets on the same wing can be covered by the same pieces; a target on each wing cannot. This is why the outside passed pawn is the most brutal winning device in king and pawn endings: the pawn itself is a decoy that will never promote, but the defending king must go to the edge of the board to stop it, and while it is gone your king eats everything else.
Same idea, different material: a bishop on a long diagonal escorts a passed pawn on one wing while guarding the entry square of the enemy passer on the other. The knight facing it can serve only one wing per four tempi, which is the mechanism behind our “Good Bishop vs Bad Knight” drill.
In rook endings, the two-weaknesses idea is why an extra pawn on one wing usually draws (there is no second front to open) and why the same extra pawn wins when the pawns are split. If your opponent's pawns are all on one side, expect a fight. If they are on both, expect blood.
How to create the second weakness
Three practical methods. Advance a pawn on the untouched wing until the defender must fix it with a pawn move, and that pawn is now a target on a color he cannot change. March the king to the far side (nothing creates a weakness like a king arriving where nobody expected it). And force the trade that leaves him with a pawn on the wing he cannot defend.
The order matters, and it is exactly the “do not hurry” order: improve everything first, then open the second front, because once the second front exists the defender may generate counterplay if your first-wing bind is loose.
The drills below are graded versions of this. The pawn endings show the decoy mechanism in its purest form. The rook ending with pawns on opposite wings shows the defensive side: how thin the hold is when the fronts are split, and how a single tempo decides who breaks first.
Questions
What is the principle of two weaknesses in chess?
It is the endgame rule that a single weakness in the opponent's camp is usually defensible, so the winning plan is to create a second weakness far from the first. The defense cannot cover both, and the extra tempi spent shuttling between them are what convert the advantage.
Who formulated the principle of two weaknesses?
The idea goes back to Wilhelm Steinitz and Aron Nimzowitsch, but it is best known from Mark Dvoretsky's endgame writing, where it appears as one of the named principles of technique alongside “do not hurry” and schematic thinking.
Why is the outside passed pawn so strong?
Because it manufactures the second weakness by itself. The defending king has to walk to the edge of the board to stop it, which leaves the pawns on the other wing undefended. You never intend to promote the outside pawn: you trade it for everything on the far side.
Does the principle apply if all the pawns are on one wing?
Much less. With every pawn on the same side there is no distant second front to open, which is exactly why an extra pawn in an all-on-one-wing rook ending is so often a draw. Creating distance (usually by advancing or trading into a split pawn structure) is part of the winning plan.
Don't just read it, play it
Every position below is playable right now, free, no signup, against a tablebase-perfect opponent that never gives up and explains every mistake.
The Outside Passed Pawn
White to play and win
Good Bishop vs Bad Knight
White to play and win
The Wing Pawn Is Bait
White to play and win
One Tempo for the a-Pawn
Black to play and draw
Practice all 62 king & pawn positionsFollow the full curriculum (free)or sharpen these endings in rated drills