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The Pawns Alone

Sometimes, because of events in other parts of the board, pawns are left on their own against the enemy King. When this happens, knowing one single rule will be enough to decide the game.

The Rule Of The Square

How can you tell if the enemy king can catch your pawn? One way is to calculate in your head, from the positions below:

"If I move my pawn to e6, then the king moves to c6, my pawn to e7, the king to d7, my pawn to e8 and I get a queen, but then the king takes my queen."

This works, as you see, but it's long and gives you too many chances to make a mistake. A second way is to count moves:

"Let's see, my pawn on e5 queens in 3 moves, while the king on b5 requires 3 moves to get to the queening square."

This is simpler, but you can still get confused. If both numbers are the same, as in the first example below, the pawn can't queen. But what if the pawn is one move closer than the enemy king? Will it still win? Look at the second position below and work it out for yourself. (Answer: only if it is the pawn's turn to move; if the King moves first the queen will not survive.)

There's an even simpler method, though. One that doesn't involve either move calculation or counting. Draw an imaginary line coming out of the front corner of the pawn's square nearest the enemy king, continuing forward and to the edge of the board, to the square with the white "X", in the example positions below.

The pawn's square and the square where that line ends will form the corners of a larger square. If the enemy king is in that square, or can move into that square, the king can catch the pawn.

X

In this position, the enemy king is inside the box, so no matter who is to move, the king will catch the pawn.

X

In this position, the enemy king is not inside the square, so if it is white to move, the pawn will queen. But, with Black to move, the king can move to b5, which is in side the square, so the pawn would not be able to queen safely.

Multiple Pawns

This rule is even more useful when you have more than one pawn, because you can use that rule to protect your pawns when your king is away from them. For example, when pawns are connected, the forward pawn is obviously protected by its partner but what can protect the backward pawn? Even alone against a king, the forward pawn can protect its partner:

So we see the pawn on d4 cannot be captured, even though it seems undefended, because to capture it the king would have to move out of the square of the e-pawn, and the e-pawn would then win the race to queen. Even though the d-pawn seems to be undefended, the Rule Of The Square defends it.

Neither of these pawns can force their way through to queen on their own, however. All the enemy king needs to do is move back and forth from d5 to e6 and back, and neither pawn can move without being captured. But this isn't always the case.

In the next position, the two pawns are one square apart. Usually, this makes them weaker, as neither pawn is obviously protected. But when facing a lone king, these pawns are protected, by the Rule Of The Square:

This technique can also be used to promote pawns that are farther away from the queening square, so long as white's king has a free square to move to:

Note pawns that are separated are only protected if the king cannot get in between them. The above example works only because the enemy king cannot get to a square on the b-file between the pawns. Separate the pawns by another file, and they will only be successful on their own if they are close enough to the queening square:

One final note about the Rule Of The Square. It works all the time, so long as the enemy king has an unimpeded path to the queening square. But if you can arrange to block the path of the enemy king, you can force it to step outside the square, and queen your pawn:

[White "White"] [Black "Black"] [Event "?"] [Site "?"] [Date "????.??.??"] [Round "?"] [Result "1/2-1/2"] [FEN "8/8/8/3kP3/8/3P4/8/7K w - - 0 1"] {White can defend his e5 pawn by moving the d-pawn forward, but what will protect the d-pawn? The pawn on d4 will be indirectly defended — by the Rule Of The Square:} 1.d4 Ke6 {The Black king stays inside of the square, keeping either pawn from advancing.}(1...Kd4?? {and the Black king has stepped out of the square so the White pawn will queen.}) 1/2-1/2
[White "White"] [Black "Black"] [Event "?"] [Site "?"] [Date "????.??.??"] [Round "?"] [Result "1-0"] [FEN "3k4/8/4P3/2P5/8/8/8/7K w - - 0 1"] {How can white protect the e-pawn this time? Black seems to be able to approach the pawns and win them, and the white king is too far away to be of help.} 1.c6! {White offers black the choice of pawns to attack. The sting in the offer is that white will advance whichever pawn black does not attack, and the Rule Of The Square will protect the other pawn:} 1...Ke7 (1...Kc7 e7) c7 {The advanced pawn has sealed off access to the queening square, so there is nothing black can do to prevent the pawn promoting to a queen on white's next move } 1-0
[White "White"] [Black "Black"] [Event ""] [Site ""] [Date "????.??.??"] [Round "?"] [Result "1-0"] [FEN "8/8/1k6/8/2P5/P7/8/7K w - - 0 1"] {In this position, the white king is too far removed from the pawns to be of any help, but The Rule Of The Square can be used to buy time for the white king to come to the aid of the pawns.} 1.a4! Kc5 2.a5 Kc6 (2...Kc4 {and black can no longer prevent the a-pawn from queening, as the Rule of The Square shows us}) 3.Kg2 {For the moment, black has prevented the pawns from advancing, so white starts bringing the king up in support.} (3.a6?? Kb6)(3.c5?? Kc5 4.a6 Kb6) 3...Kb7 (3...Kc5 {is no better. White simply continues bringing the king towards the pawns} 4.Kf3 Kc6 5.Ke3 Kc5 6. Kd3 Kc6 7.Kd4 {and now black has to move away from the c-pawn, and white's king is closer than in the main line}) 4.c5 {Again, black must choose which pawn to move toward, and white will simply advance the other} 4...Ka6 (4...Kc6 5.a6) 5.c6 Ka7 6. Kf3 {Again, white moves the king and looks to see which pawn black will try and stop} 6...Kb8 (6...Ka6 7. Ke4 {and, as in the note above, white's king arrives on the scene to help the pawns advance.}) 7. a6 {and we have a position just like the previous one, where white queens whichever pawn black doesn't block.} 1-0
[White "White"] [Black "Black"] [Event ""] [Site ""] [Date "????.??.??"] [Round "?"] [Result "*"] [FEN "8/8/2k5/8/3P4/P7/8/7K w - - 0 1"] 1.a4 Kd5 2.a5 Kc6 3.Kg2 Kb5 {and the pawns can no longer use the Rule Of The Square to protect each other. The game will hinge on whether white's king can assist the remaining pawn, something we will cover in the next installment.} *
[White "M. Aster"] [Black "P. Atzer"] [Event ""] [Site ""] [Date "????.??.??"] [Round "?"] [Result "1-0"] [FEN "8/3p4/8/2P5/P3k3/8/8/7K w - - 0 1"] {The black king is inside the square of the white a-pawn, so it seems there is no way to force a queen.} 1. c6! {or is there?} (1.a5?? {The direct approach doesn't work, because the black king has a direct path to the queening square} 1...Kd5 2.a6 (2.c6 {doesn't work now, because of } 2...Kc6) 2...Kc6 3. a7 Kb7 {and the pawn is caught}) 1...dxc6 (1...Kd5 2.cxd7 Kd6 3.d8=Q) 2.a5 Kd5 3.a6 {Now the point of moving the other pawn first should be clear: black cannot continue on a straight path to the queening square because c6 is occupied by a black pawn. So black must detour around the pawn, and the Rule Of The Square tells us when that happens the white pawn will queen:} 3...Kc5 (3...Kd6 4.a7 Kc7 5.a8=Q) (3...c5 {to try and force a black queen is no better} 4.a7 c4 (4...Kc6 5.a8=Q) 5.a8=Q) 4.a7 Kb6 5.a8=Q