How to checkmate with two bishops

Two bishops on adjacent diagonals cover a barrier no king can step over. Build the wall, walk it forwards, and mate in a corner.

Worst case, perfect play: 19 moves
You are allowed 50
Every trainer position a proven forced win
Free practice, no account

Practise this against a king that defends A fresh position every time, generated and verified. The defending king takes anything you hang and will not step into mate in one, so the only thing that finishes the game is your technique. Open the trainer

What the mate looks like

Start at the end. Every basic mate happens on an edge or in a corner, and it is worth knowing the finished picture before learning the moves that produce it.

Checkmate. The black king on h2 is in check from the bishop on f4. It has five squares to try and none of them work: g1 and g3 are covered by the king on f2; h1 and h3 are covered by the bishop on g2; the bishop on g2 cannot be taken, because the king on f2 defends it.

Where it started, 15 moves earlier. The shaded squares are the box: everywhere the black king could still walk to if White stood still. There are 22 of them. Making that number fall is the entire ending.

The idea

One bishop can only ever see half the board, which is why one bishop and a king cannot mate at all. Two bishops on opposite colours between them see everything -- and when they stand side by side on adjacent diagonals they form an unbroken diagonal wall. The enemy king cannot cross it anywhere.

The ending is therefore simple to describe and fiddly to execute: build the wall, walk it forwards with your king behind it, and squeeze the enemy king into a corner. It is a corner mate, always, because a bishop cannot take away the square next to it and the king has to run out of board in two directions at once.

The method

Get the bishops side by side. Two bishops on adjacent diagonals, next to each other or one square apart on the same rank, cover a line of squares the king cannot cross.
Bring your king. It goes behind the wall and it is doing the real work: the bishops hold the line, the king takes the squares next to the enemy king.
Walk the wall forwards. One bishop moves, then the other, keeping them on adjacent diagonals, each pair of moves taking a rank or a file away from the enemy king.
Drive towards a corner. Any corner will do -- unlike bishop and knight, both corners of both colours are available, because between them the two bishops cover every square.
Mate. The enemy king in the corner, your king two squares away facing it, one bishop giving check along the diagonal into the corner and the other covering the escape square beside it.

A worked example, move by move

The position on the right above, played out. This is not a line somebody typed in: it is the shortest forced mate that exists from that position, taken from a tablebase built for this page, with Black defending as well as it is possible to defend.

The box columns are the squares the black king could still walk to if White stood still. It starts at 22 and the mate is played when it is one. It does not fall smoothly: four of White's 15 moves here leave the king more room than it had, not less. That is real and it is worth understanding. A tablebase plays the shortest mate it can find rather than the most teachable one, and it can afford a move that opens the box because it can already see the finish. You cannot, which is why the method above trades a few moves for a box that mostly only shrinks. Bishops cut diagonals, so the region they leave is an awkward shape and it changes a lot when either of them moves. The wall is easier to see on the board than in the number.

After 7 moves. The box is 6 squares, down from 22. Nothing dramatic has happened; the king simply has less room than it did.

Mate on move 15. The box is one square, the king is standing on it, and it is in check.

Show the whole line

	White	Box	Black	Box
1.	Kg7	18	Kf4	18
2.	Kf6	19	Kg3	19
3.	Bf1	26	Kf4	26
4.	Bd3	11	Kg3	11
5.	Kf5	31	Kf3	31
6.	Bf1	24	Kg3	24
7.	Be2	6	Kh3	6
8.	Kf4	5	Kh4	5
9.	Bf2+	20	Kh3	19
10.	Bf1+	3	Kh2	2
11.	Be3	2	Kh1	2
12.	Kf3	2	Kh2	2
13.	Kf2	2	Kh1	2
14.	Bg2+	2	Kh2	1
15.	Bf4#	1	—	—

Replayed through the same rules engine the app runs on. The final position is called checkmate because isCheckmate() says it is.

What goes wrong

Letting the bishops drift apart. Two bishops on distant diagonals leave a hole, and the king walks through it. If you cannot see the wall, there is no wall.
Leaving your king behind. The bishops confine; the king mates. Every move where your king is not getting closer is a move you have to make up later, and the worst case here is 19 moves out of fifty.
Stalemating in the corner. Real and common. The king in the corner with both bishops covering everything and no check is a draw. Count the squares before you move.
Trying to mate in the middle. It does not exist. The mate needs two edges, which means a corner.

How long you actually have

Fifty moves. Under the fifty-move rule a game is drawn on request once fifty moves pass with no capture and no pawn move, and in an ending like this one nothing is ever captured, so the count runs from the moment the last piece came off the board.

Working backwards from every checkmate position that exists with these pieces until every position has an exact answer gives the real worst case: 19 moves with perfect play on both sides from the least convenient starting position there is. That leaves a comfortable margin, but it is the first of these endings where a wandering start can genuinely cost you the win.

Practise it

Reading the method is the easy half. The trainer below the fold on the practice page gives you a fresh generated position, a defending king that does not help you, a live count of the box, and a move budget of 34 for this ending -- 15 more than perfect play would need.

How to checkmate with two bishops, for real Free, no sign-up, works offline. It warns you before you stalemate and explains it if you do. Practise two bishops

Questions people ask

How do you checkmate with two bishops?

Put the bishops on adjacent diagonals so they form a wall the enemy king cannot cross, bring your own king up behind it, and walk the wall forwards one rank at a time until the king is in a corner. Mate is one bishop checking along the diagonal into the corner while the other bishop and your king cover the two escape squares.

Can two bishops checkmate a king?

Yes, provided they are on opposite colours, which two bishops that started the game together always are. King and two bishops against a lone king is a forced win from any legal position. Two bishops on the same colour, which can only happen after a promotion, cannot mate at all.

Is the two bishop checkmate hard?

It is the third hardest of the five basic mates and much easier than bishop and knight. The worst case with perfect play is 19 moves against fifty allowed, so there is room for imperfect technique, but not for aimless technique.

What is the two bishops checkmate called?

It does not have a settled name of its own. The finished position, where two bishops cut a king's escape on adjacent diagonals, is sometimes called the double bishop mate, and that pattern shows up in the middlegame too.

The other basic mates

Five endings, one page each, all of them forced wins.

Elsewhere on the site: endgame tactics from real games, mate in one for seeing a mate before forcing one, stalemate and the opposition in the glossary, and free printable worksheets for clubs and classrooms.