Key Squares

Knowledge of Key Squares is absolutely vital in even the simplest King and Pawn endings!

Your Turn!

Find the win:
The classic mistake of 1...g3?? is seen far too many times!

Why is 1...g3 so bad?

  • The defender has more scope than after the winning move 1...Kg3! when the defending king has to give up ground!
  • After 2. Kg2! black is really struggling to convert the pawn - in fact, cannot, if the defender sticks to key principles
  • g3 is a "Key Square" - we'll see what this means very soon!
For reference, 1...Ka3 also wins after 2. Ka1 b3 ("the squeeze") 3. Kb1 b2 (the king is literally squeezed out of the 1st rank) 4. Kc2 Ka2 with 5...b1=Q to follow.

A key can unlock many doors - do you know where to find them?

Even the basic understanding of key squares will convert more draws to wins and save a few more games as a defender!

Three things you will learn today

  1. Which squares are key squares and why
  2. Tricks with the B and G pawns!
  3. How to defend K+P endings

Part 1 of 3 - Identifying key squares

Rook Pawns

Let's start with the exception - the rook files. With a single pawn on the a or h file against a king, it is the most challenging to win.

[Event "Example - King v Pawn & King"] [Site "Chess Toolkit (Author = TQM.)"] [Date "12/03/2017"] [White "Player, A"] [Black "Opponent, Anne"] [Result "0-1"] [ECO "N/A"] [Annotator "TQM"] [SetUp "1"] [PlyCount "44"] [EventDate "2017"] [FEN "8/8/8/7p/8/5k2/8/4K3 b"] 1...Kg2! (1...Kg3?? {draws as the defending king can either hide in the corner or trap the attacking king on the h file:} 2. Kf1! Kh2 {else the king reaches g1 then h1} (2...h4 3. Kg1 h3 4. Kh1 h2 {draw}) 3. Kf2 h4 4. Kf1 h3 5. Kf2 Kh1 6. Kf1! h2 7. Kf2 {and it's a draw!}) 2. Ke2 {white is just dead lost} h4 3. Ke3 h3 4. Kf4 h2 {and black wins}
From the example we can see that unless the defender can easily take the pawn, the key squares were g1 and g2. If the attacking king can get there, the defender cannot reach h1 in time to defend.

Similarly, for the h8 advance, the key squares are g7 and g8 and similarly [a1; b1-b2] and [a8; b7-b8]. These key squares don't depend on where the pawn is.

Central Pawns (b to g files)

The technique for central pawns is much simpler to remember but there is a sneaky point for b and g pawns we'll see in the end of this section to be mindful of!

Your Turn!

The ONLY solution here is 1. Kb4! Even from first inspection, the attacker has more options for the king than the alternatives, so logically is a good starting point for analysis.

This might seem amazing with so many potential lines to analyse but there is a shortcut to do the analysis.

The defender only wants to be able to squash the attacking king to within one square of his pawn, making the defensive task much easier! With, for example, 1. c3?? Kc5! and white cannot make any further moves without the defending king being annoying close.

Let's look at how to win after 1.Kb4!

[Event "Example - King v Pawn & King"] [Site "Chess Toolkit (Author = TQM.)"] [Date "12/03/2017"] [White "Player, A"] [Black "Opponent, Anne"] [Result "1-0"] [ECO "N/A"] [Annotator "TQM"] [SetUp "1"] [PlyCount "44"] [EventDate "2017"] [FEN "8/8/8/3k4/8/1K6/2P5/8"] 1. Kb4 (1. c3?? Kc5 2. Kc2 Kc4! 3. Kd2 {and black will hold - see section 2})(1. c4?? Kc5! 2. Kc3 Kc6 3. Kd4 Kd6 {and white is squashed up against his pawn})(1. Kc3 Kc5! {and we tie the king within one square of its pawn - drawing!}) 1...Kc6 (1...Kd4 2. c4 Ke5 3. Kc5! {pushing the king further away!} Ke6 4. Kc6! Ke7 5. Kc7 Ke6 6. c5 Kd5 6. c6 {and plain sailing!}) (1...Kd6 2. Kb5 Kc7 3. Kc5 {as in the mainline but with more tempi to use!}) 2. Kc4! {zugswang to gain space} Kb6 (2...Kd6 {is the same idea}) 3. Kd5 {called outflanking; gaining space} Kc7 4. Kc5! {zugswang again!} Kc8 {we've seen the outflanking idea after 4...Kb7 5. Kd6 etc.} 5. Kc6! {final zugswang} Kd8 6. Kb7 Kd7 7. c4 {we make our first pawn move!!} Kd6 8. Kb6 Kd7 9. c5 Kc8 {trying to prompt 10. c6?? Kb8, drawing} (9...Kd8?! 10. Kb7!) 10. Kc6! Kb8 11. Kd7 Kb7 12. c6 {and the pawn queens}
We have seen the technique for winning and how giving the king the best scope is best but what are the key squares?

  • For the a and h pawns they are the equivalent g1 and g2 squares (in instance of h1 target)
  • For the central pawns we have two cases:
    1. if the pawn is in the bottom half of the board, our key squares are the three squares two ranks ahead - e.g. for the example above with pawn on c2, they are b4-d4. Otherwise the defending king can tie our king to within 1 square of the pawn.
    2. If the pawn is in the second half of the board, it is even the rank ahead of the pawn and two ranks ahead. This is because we can already use the "squeeze" when the pawn is on the 5th to time the advance to squeeze the defending king off the 8th:

Summary of Part 1

The king and pawn ending is won provided:
  • The pawn can queen (or become a rook!) either supported or unaided
  • To support the pawn, the king must reach a key square
  • Rook pawns have key squares on the two neighbours to the h1 equivalent (g1,g2)
  • Central pawns - bottom half, key squares are two ranks ahead; top half, one rank ahead is already a key square!

Part 2 of 3 - Tricks with the B and G pawns!

[Event "Example - King v Pawn & King"] [Site "Chess Toolkit (Author = TQM.)"] [Date "12/03/2017"] [White "Player, A"] [Black "Opponent, Anne"] [Result "1-0"] [ECO "N/A"] [Annotator "TQM"] [SetUp "1"] [PlyCount "44"] [EventDate "2017"] [FEN "1k6/8/1K6/1P6/8/8/8/8"] 1. Ka6 {this is the best case scenario for the defender - white is put in zugswang but can still win!} (1. Kc6?! {THIS IS VERY IMPORTANT - this innocent move doesn't work, due to a stalemate trap:} 1...Ka7! 2. b6?? {just start again with 2. Kc7 Ka8 3. Kb6 Kb8 4. Ka6!} 2...Ka8 {and white has stumbled into a draw!!} 3. b7 (3. Kc7 {is stalemate}) Kb8 4. Kb6 {is stalemate!}) 1...Ka8 2. b6! Kb8 3. b7 {and white wins}

Summary of Part 2

The king and pawn ending is won on the B and G files, however:
  • To support the pawn, the king must reach a key square
  • The attacker must avoid the Kc6 trap!
  • If you play Kc6, repeat the moves to get back to the starting position!

Part 3 of 3 - Defending K+P endings

Because of what we've learned in sections 1 and 2, the defensive task can be broken down very easily:
  1. Don't get in a position where you can be squeezed!
  2. Don't let the attacking king get to a key square!
  3. Play dirty with the B and G pawns - it's easy for the attacker to go wrong!
In the next example, the king has missed his chance to get to key squares, we just have to hold!

Avoiding the Squeeze!

[Event "Example - King v Pawn & King"] [Site "Chess Toolkit (Author = TQM.)"] [Date "12/03/2017"] [White "Player, A"] [Black "Opponent, Anne"] [Result "1/2-1/2"] [ECO "N/A"] [Annotator "TQM"] [SetUp "1"] [PlyCount "44"] [EventDate "2017"] [FEN "4k3/8/4P3/4K3/8/8/8/8 b"] 1...Ke7! {only move} 2. Kd5 Ke8! 3. Kd6 Kd8 4. Ke5 Ke7 5. Kf5 Ke8! (5...Kf8?? 6. Kf6! Ke8 7. e7 {and black is squeezed out!}) 6. Kf6 Kf8! 7. e7 Ke8 8. Ke6 {stalemate}
The defender simply has to make sure when the attacking king hits the 6th rank, we get to the corresponding square on the 8th (d6,d8) or (f6,f8).

Denying Key Squares

Given our earlier knowledge, the devastating 1...a4!! will break white's heart.
  • Accepting the pawn with 2. bxa4 is a dead draw with our king just running to the corner or hogging the a file.
  • 2. b4+? draws trivially
  • 2. Kc2 allows 2...axb3 3. axb3 (3. Kxb3 is a rook pawn ending which is hopeless here) and black defends easily by keeping the white king pegged to the b3 pawn!
  • 2. Kc3 equally runs into 2...axb3 3. axb3 Kb5 and white still makes no progress.

Summary of Key Squares

  • Knowledge of key squares is vital and eliminates mountains of calculation.
  • Attackers must try to get to a key square; defenders must prevent that happening
  • Central pawns are easiest to convert but B and G pawns are sneaky (play 1. Ka6!, not 1. Kc6?!)