In the search for answers beyond immediately threatening back rank mates. How early is it possible to spot that you'll have problems down the aisle, from a strategic perspective? What are the defining characteristics of this position?
This puzzle from chess.com shows a back rank weakness:
[FEN "3r1k2/1p5p/pqn1Qpp1/5n2/8/5BP1/PP3P1P/4R1K1 w - - 0 1"] 1. Qxf6+ Kg8 2. Bd5+ Rxd5 3. Re8#
It shows that:
- The heavy pieces have to exploit the weak back rank
- To exploit the weak back rank, there has to be at least one open file
- A sacrifice (2. Bd5+) may be needed to lure away a defender
- The weak back rank is typified with there being no escape for the king if it is checked
Back rank mate is the most common checkmate. The earliest when you need to think about it is when:
- Heavy pieces are still on the board
- Files are being opened
- The defending rooks are leaving the back rank (maybe deflected, exchanged off, going to the centre etc.)
- When the king has castled, usually kingside, with no luft having being made e.g. black hasn't played ...h6
One of the most famous chess games ever. Both sides have back rank mates!
29...Qb2!! (0-1) wins the game for Black by back-rank mate
- None of the king-side pawns move
- Both kings are behind the pawns and have no escape square
- There are open-files on the board
- Both side has a rook and a queen exploring the open files
- No white rook on the back rank defending (the white rook is on the third rank)
- The white queen is the only piece guarding the f1 square
The main hallmark of a weak back rank is that your king is hemmed in by pawns, pieces, or squares controlled by your opponent so that it can only move sideways. It may also have insufficient defenders (rooks or queen) or defenders may be blocked from defending the king by other pieces.
But the back rank is nearly always weak - what you need to watch out for is opportunities your opponent has to exploit that weakness. For example, their rook is on an open file or a file that can be opened by a tactical maneuver or sacrifice. A weak back rank can really only be exploited by your opponent's rooks or queen, so keep an eye on them, and on the availability of escape squares for your king. You basically never want those guys on your back rank if you can help it.
Yet it can also be a mistake to waste a tempo you could have used for attack to prevent a potential back rank threat that may never come, or to weaken your pawn structure in front of the king just to give him an escape square. This is why back rank threats remain such a common motif.