The Back Rank Mate happens when a king is trapped behind its own pawn shield and gets mated by a rook or queen.
Back Rank Mate Example 1
Diagram above: White plays 1.Rd8# The black king is trapped on the back rank, behind his own pawn shield, hence the name “Back Rank Mate”.
Back Rank Mate Example 2
Diagram above: White plays Rd8#. A typical Back Rank Mate. Note that the black king cannot escape to the g7-square, because white’s bishop on a1 has it covered.
In most situations the pawn shield does a great job to protect the king, but you should be aware of the potential back rank weakness. One way to deal with this weakness is to play a move known as creating “luft” (German word for “air”), a chess term which means you open an escape square for your king, usually by advancing the g-or-h-pawn one square.
Diagram above: Black plays 1… h7. This move creates an escape square for black’s king and prevents the possible Back Rank Mate.
However, as you just in the previous example, this idea isn’t effective if your opponent has the escape-square covered.
Important Notes on the Back Rank Mate
The Back Rank checkmate pattern is proof that your own pieces can sometimes work against you and help your opponent achieve their objective! It is the source of a common tactical idea know as a back rank weakness.
When you take advantage of a potential Back Rank Mate, without actually delivering the checkmate, it’s known as “exploiting the back rank weakness”.
Diagram above: White plays 1.Bxa6 and wins the bishop. The point is that white takes advantage of black’s back rank weakness. Black can’t recapture the bishop, 1… Rxa6, since that would allow white to perform the Back Rank Checkmate with 2.Rd8#
More Back Rank Mate Examples
ChessCoachClark on chessgames.com, keeps a list of actual games where the Back Rank Mate (or back rank weakness) played a decisive role in the game. The Wikipedia page on Back Rank Checkmates also gives a few instructive examples.