Bishop and Pawn vs Bishop
With same-colored bishops, bishop and pawn against bishop is a draw whenever the defending king reaches the pawn's path — park the king on a square the enemy bishop cannot attack, and no technique in the world makes progress. When the king is cut off, the defending bishop fights alone, and the verdict depends on geometry first analyzed by Centurini in the nineteenth century: the bishop holds if it can watch the pawn's key square from a long enough diagonal, and loses if the attacker can block that diagonal on a square his king protects. All three boundary positions below are tablebase-verified.
This page covers the same-colored case, which is where all the content lives. With opposite-colored bishops a single extra pawn is a trivial draw — the defending bishop simply parks on the promotion square's color and can never be challenged — and that story belongs to opposite-colored bishop endgames.
First Line of Defense: The King in Front
The defender's first goal has nothing to do with his bishop. White: Ke5, pawn e6, Bd3. Black: Ke7, Ba8 — light-squared bishops, black king on e7, directly on the pawn's path and on a dark square. Black to move, dead draw:
The geometry is airtight. The king on e7 blocks the pawn and stands on a dark square, so White's light-squared bishop can never attack it or even give a check that matters. The white king can never touch e7 either — d6 and f6 would put it next to the black king, which is illegal. So what is the black bishop for? Tempo duty. Black shuffles 1...Bb7, 2...Ba8, 3...Bb7 forever; White can never put Black in zugzwang, because the bishop always has a spare tempo on the long diagonal. That is the quiet, essential job of the defending bishop in this setup — not to fight, but to pass.
One warning, verified by the tablebase: from the diagram, the only losing idea is leaving the path — 1...Ke8? loses to 2.Kd6!, when the white king finally comes around the pawn and Black's pieces cannot cope. The front square is the fortress; hold it and nothing else matters. If the pawn stood on a square of the bishops' color instead, the same logic holds with the king one square further back on the promotion path — what matters is a path square the enemy bishop cannot attack.
The King Cut Off: Centurini's Battlefield
Everything interesting happens when the defending king is driven away and the bishop must stop the pawn alone. The bishop's method is to control the promotion square (or the pawn's next square) from a distance. The attacker's method is interference: put his own bishop on the defender's diagonal, on a square his king protects, cutting the defender's view — a pure application of the interference motif. Whether that plan works is a question of diagonal lengths, and the two positions below sit on either side of the boundary.
The win. White: Kc6, pawn b7, Bc1. Black: Kg8, Bg3 — dark-squared bishops. The black bishop guards b8 from the long h2–b8 diagonal, but the other diagonal through b8 contains only one square, a7. White to move wins:
1.Ba3! heads for the interference square. 1...Bb8 is the most stubborn defense — the bishop leaps inside the blockade — but 2.Bd6! attacks it on a square protected by the king on c6, and after 2...Ba7 the defender has been pushed off the long diagonal onto the one-square diagonal a7–b8. Now the deflection is elementary: 3.Kb5 Kf7 4.Ka6 attacks the bishop, and since a7 was its only square that still guards b8, 4...Bf2 5.b8=Q ends it. The whole mechanism in one sentence: block the long diagonal with a protected bishop, then evict the defender from the short one with the king.
The draw. Move the same fight two files toward the center and the defense holds. White: Ke6, pawn e7, Bf1. Black: Kh8, Ba4 — light-squared bishops, and the black bishop watches e8 along a4–b5–c6–d7. White to move cannot win:
Try Centurini's recipe: 1.Bb5 interferes on the diagonal — but here the square is not protected by the white king, so Black simply plays 1...Bxb5!, and the promotion never sticks: 2.e8=Q+ Bxe8 and the new queen comes straight off the board (3.Kxe8 is impossible — the king on e6 is not close enough). Count the squares and you see why no interference works: the defender's diagonal a4–d7 has four squares. The interference points b5 and c6 are too far from the pawn for White's king to protect, and the one point the king does cover, d7, can never be occupied — White's own bishop has no road there, and the white king cannot step onto d7 itself because the black bishop attacks it. Four squares is enough room; one square (a7 in the previous diagram) is not.
This yields the practical version of Centurini's rule: with the defending king cut off and the pawn on the sixth or seventh rank, the defense holds when the bishop can operate on a diagonal of at least four squares against the pawn's key square; it loses when it can be forced onto a short diagonal, because every square there lies within the attacking king's protective reach. Central pawns leave the defender a long diagonal on at least one side and usually draw; knight pawns like the b7-pawn above leave a one-square diagonal on the edge side and usually win. Rook pawns are their own world: with the wrong bishop the game is drawn no matter what, and with the right bishop the defense still holds easily if the defending king reaches the corner.
The Practical Map
For over-the-board decisions, compress all of this into a checklist. Defending: race your king to the pawn's path first — that draw requires no memory. Failing that, put your bishop on its longest available diagonal against the pawn's key square, keep it as far from the action as that diagonal allows (distance is immunity from the enemy king), and remember you can always give the bishop for the pawn the instant a fork or a trade threatens — bishop versus bishop is a trivial draw. Attacking: drive the king off the path before advancing the pawn to the seventh; identify which of the defender's two diagonals is short; and execute the two-step — protected interference on the long side, king attack on the short side. If both of the defender's diagonals are long, save your energy: the position is a book draw, and the real winning attempt should have happened earlier, in the full same-colored bishop endgame, before the position simplified this far. And before any bishop trade that wins the pawn's blockade, verify the resulting king and pawn vs king position — the pawn ending, as always, is the court of final appeal.
Frequently Asked Questions
Is bishop and pawn versus bishop a draw?
With same-colored bishops it is a draw whenever the defending king stands on the pawn's path on a square the enemy bishop cannot attack, and also when the defending bishop has a long diagonal against the pawn's key square. It is winning chiefly when the defending king is cut off and the bishop can be forced onto a short diagonal, as with a knight pawn on the seventh.
What is Centurini's rule?
Luigi Centurini analyzed these endings in the 1850s and established the governing principle: with the defending king cut off, the attacker wins by blocking the defender's long diagonal with his own bishop on a protected square, then using the king to evict the bishop from the short diagonal. The defense holds when the defending bishop's diagonal is long enough — in practice at least four squares — that no interference square can be protected.
Why does the defending king want to stand on the opposite color from the bishops?
On a square of the opposite color, the king can never be attacked or checked by the enemy bishop, and the enemy king cannot approach a defended king square. The blockade is then permanent: the attacker has literally no piece that can contest the square the king occupies.
What is the defending bishop actually doing in the king-in-front draw?
Burning tempi. The fortress square is held by the king; the bishop's job is to make endless safe waiting moves so the defender is never in zugzwang. That is why the defending bishop belongs on a long, quiet diagonal far from the enemy king rather than actively attacking anything.
Does the pawn's file matter in these endings?
Enormously. Central pawns give the defending bishop at least one long diagonal and usually draw even with the king cut off. Knight pawns leave a one-square diagonal on the edge side and are the attacker's dream. Rook pawns with the wrong bishop are always drawn, since the defender's king only needs to reach the corner.
With opposite-colored bishops, is the single pawn ever winnable?
No — the defender puts his bishop (or king) on the promotion path's other color and can never be dislodged, since the attacking bishop does not operate on those squares. That total immunity is exactly why defenders steer for opposite-colored bishops when down a pawn.