Why do I keep missing mate in one?

Almost always because you never considered the move. Players scan for checks with the piece they are already thinking about, and the mate is delivered by the other one, or by a capture that looks like it just loses material. Listing every check, in order, without judging any of them, fixes most of it.

Does mate in one always involve a check?

Yes. Checkmate is check plus no legal reply, so the mating move must give check. That is what makes mate in one searchable: you only have to look at checks, which is usually three or four moves out of forty.

How long should a mate in one take me?

Under ten seconds once the habit is in place, and that is the point of drilling them. Speed on one-movers is what lets you calculate longer lines, because you recognise the end of a variation instantly instead of working it out square by square.

How to find mate in one

Start here. White has two checks in this position, one with the bishop on b3 and one with the rook on d1, and exactly one of them is mate.

White to play and mate in one. The two checks are Bxf7+ and Rd8. Only one ends the game.

1.Bxf7+ is the check most people see first, because a capture with check feels like progress. Count the king’s squares afterwards: he takes the bishop, Kxf7, and White has thrown away a piece for nothing.

1.Rd8 gives no material, takes nothing, and wins on the spot. The rook covers the whole eighth rank, so f8 and h8 are gone; f7, g7 and h7 belong to Black’s own pawns; nothing on the board attacks d8; there is no square between d8 and g8 to block on. That is a mate.

The method, in three questions

Find every check first. All of them, including the ones that hang a queen, before you evaluate any of them. Write them down if you are training. In the position above the list runs to two, Bxf7+ and Rd8; in a normal middlegame it is usually three or four, which is a small enough list to be honest about.

Then for each check in turn:

How many squares can the king move to? Count them out loud if you can, and remember that a square occupied by his own piece is as good as a covered square for your purposes.
Can anything capture the checking piece? Include the king himself, which means asking whether your checking piece is defended.
Can anything get in between? Only applies to checks by a rook, bishop or queen along a line. A knight check can never be blocked.

Three noes means mate. One yes means move on to the next check. This is slower than intuition for about a week and then it stops being slow at all.

Question two is where the mates hide

Here is the same drill with the answer sitting behind the second question, and this time both checks land on the seventh rank.

White to play. Qxh7+ is met by Kxh7. Qxg7 is mate, because the bishop on b2 defends the queen along the long diagonal.

Two checks again: 1.Qxh7+ and 1.Qxg7. They look almost identical. The first loses the queen to 1…Kxh7, because nothing defends h7. The second is mate, because the bishop on b2 stares down the long diagonal to g7 and the king cannot take. After 1.Qxg7 the king’s remaining squares are f8 and h8, both covered by the queen from g7, and f7 and h7 hold his own pawns.

Same shape, g7 and h7 one square apart, opposite results. The question that separated them was not “is this a check” but “who is defending the square I am landing on”.

Drilling it

Do them in volume and at speed. Twenty mate-in-one puzzles a day for two weeks will change how quickly you see the end of a line, and the patterns you meet there, the back rank above all, are the same ones that decide your own games. When a one-mover takes you more than a few seconds, stop and work out which of the three questions you skipped.