I suspect that almost every player who has looked at a beginner's book covering endgames has seen this position:
What's remarkable is that although White has no passed or even unopposed pawns, and the Black pawn structure has no weaknesses, White can nonetheless win with 1.b6! axb6 2.c6! bxc6 3.a6 (or 1...cxb6 2.a6! bxa6 3.c6). It seems like alchemy, but incredibly, it works!
Note that with Black to move in the starting position, only 1...b6! will save him - 1...a6? 2.c6! bxc6 3.b6 (or 1...c6? 2.a6! bxa6 3.b6) wins, reminiscent of the
tactical trick in the previous post. After 1...b6!, none of White's tactical tricks are possible, so it comes down to the placement of the kings, which in this case ensures a win for Black.
A second note: while 1...a6 and 1...c6 both lose, with Black to move, if Black could play
both moves, then he would be fine,
even if we gave White an additional a, b, or c-pawn! (Unless one puts the pawn on a7 or c7, that is, but we're ignoring bughouse-ish possibilities here.) One application of this comes in the Exchange Variation of the Ruy Lopez, when after 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6 5.O-O f6 6.d4 exd4 7.Nxd4 c5 8.Nb3 Qxd1 9.Rxd1 etc. White's endgame fantasy is to trade off all the pieces and head for a pawn ending. White's 4-3 kingside majority is healthy and will result in a passed e-pawn, but Black's queenside majority can be stymied by placing pawns on a3, b2, and c3, and then only recapturing Black queenside pawns, never initiating the capture.
With all this by way of background, consider the following position, also, ironically, from another 1-minute game played the same night as the previous post's game:
My queenside pawn structure is healthier than Black's, but the most important feature of the position is the Black king's encroachment on my side of the board. If it were Black's move, we might see 1...Kh2 followed by 2...Bc5 3.Be1 (3.Bxc5 volunteers for a hopeless pawn ending after 3...bxc5, 4...Kh3 followed by ...Kg4xf4) Kg1 followed by ...Kf1. Maybe I can keep him from penetrating all the way to my queenside, but that sort of worry motivated my move in the game:
1.Bg3?
Maybe I'm losing anyway, but there's no question about it after his next move -
1...Bh4!
now I'm completely lost! After the forced
2.Bxh4 Kxh4
all my opponent needs to do is place me in zugzwang, so that my king has to allow ...Kg4, and then allow ...Kxf4. In part to delay (it is 1-minute chess!), and in part hoping for some sort of happy accident, I continued
3.b4
Here the hideous 3...a5?? loses to 4.c5! (again, remember the previous post), but 3...c5 and 3...b5 essentially terminate resistance. My opponent's choice didn't lose, but kept a spark of hope alive:
3...a6 4.a4
I trust everyone sees where this is going. 4...a5?? and 4...c5?? are horrible, due to 5.c5 and 5.a5, respectively, but Black's best move is 4...b5!, when, objectively speaking, resignation is required. Perhaps my opponent thought, in the constant time pressure that is 1-minute chess, that it was best to avoid pawn contact over there unless absolutely necessary, and decided to mark time with his king. Besides, the breakthrough strategy of the first diagram only works when White's pawns start a rank further up, right?
4...Kh3?? 5.b5 axb5 6.c5 bxc5 7.a5 b4 8.a6 b3 9.a7 b2 10.a8Q b1Q
We've both queened and Black has two extra pawns, but there's a little problem:
11.Qh8#
The moral of this story is that the trick from the first diagram can be effective even when the first move is 1.b5 rather than 1.b6, depending on the placement of the remaining material, especially the kings. Apply what you know!