The Open File - Retrograde Help, Mate!

Submitted by NM Zug on Mon, 09/22/2008 at 10:20am.

The Open File

by Life Master Mike Petersen (Zug)

Retrograde Help, Mate!

How many of you have ever heard of retrograde analysis in chess? Well, if not, then you're in for a treat. The basic idea is this. A position is set up on the board, and you are to guess what the last couple of moves were in the game. It's sort of like "unplaying" a position. Let me show you a couple.

Look at the position below. It is White to move. This is obviously an easy win for White, but that's not the point here. Your job is to figure out black's last move. So, give it a go and see if you can figure out what it was. Since Chess.com has no way for me to give an "unmove" solution, I will place it below the diagram, but far enough down that you won't see it unless you scroll to it.

Scroll down for solution.

Obviously, the black king must have moved from a7, moving out of check. But how did White deliver the check? With some analysis, you can see that White moved a knight from b6 to a8. Thus, the last move was for the Black King to capture a White Knight on a8.

Pretty neat, eh? Okay, here is another one. It's White to move and mate in two. The question is, what was Black's last move? Also, what was White's last move before Black's? As above, the solution is available if you scroll down.

Scroll down for solution.

First, the mate in two:

White plays Bf5 and mates by Bc8 or cxb5, depending on Black's move.

Now, the (not so easy) retrograde analysis solution:

In the position of the diagram, black played the last move. It can only have been K(on b6) capturing something on a6. The double check by the Rook on b4 and Bishop on g1 to the King on b6 is explained by the en passant capture bxc6 e.p. The previous black move is therefore c7-c5. Then the check by the Bishop on g1 can only be explained by N(on c5)xa6. So we see that the Black King captured a Knight on a6. This White Knight must have captured a Black Knight on a6 to allow a Black Knigh on b8 to capture on a6. Here ends the sequence of moves that we can deduce. So the last moves were :
White : Ka4; Rb4; Bg1, g6; Nc5; Pb5, c4, h2 : 8 (and eventually something on a6)
Black : Kb6; Nb8; Pa7, b7, c7 : 5
1. ...... Nb8(x)a6
2. Nc5xa6+ c7-c5
3.b5xc6 e.p.++ Kb6xa6 diagram.

There are many types of retrograde analysis problems. One of the more interesting ones is to show a position and ask, "Can White (or Black) castle here?" The solutions always involve retrograde analysis.

There is another interesting type of chess problem called a "Helpmate". In this type of problem, your job is to assist in the mate. A simple example is shown below. The problem is a "Helpmate" in one move. In this type of problem, Black always moves first and helps White to mate him. The obvious solution is Ke8, allowing Rh8, mate.

I have created two Helpmates of my own. I was fortunate enough to have both published in Chess Life, the monthly magazine of the US Chess Federation. They are both of my own creation. See if you can figure them out. The first is a Helpmate in two moves, and the second is a Helpmate in three moves. Remember, Black moves first.

Note that in the second problem, the Kings vacate squares for the Bishops, and each move is toward White's side of the board.

If you enjoyed solving these types of problems, there are many locations on the Internet to find them. Just Google "retrograde chess" or "helpmate chess", and you will find many more examples. Have fun!

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