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In chess, a back-rank checkmate (also known as the corridor mate) is a checkmate delivered by a rook or queen along a back rank (that is, the row on which the pieces (pawns ) stand at the start of the game) in which the mated king is unable to move up the board because the king is blocked by friendly pieces (usually pawns) on the second rank . A typical position is shown to the right. ==Introduction== Back-rank mates occur quite often in games at fairly low levels. This is because beginners typically fail to anticipate an impending mate on the back rank. At higher levels of play, though the mate itself does not occur very often, play is often affected by the possibility of it—the fact that a player has to spend time guarding against the mate may leave him vulnerable to other threats and tactical ideas. Back-rank mates are often guarded against by a friendly rook or queen protecting the back rank. However, it may be possible for the attacking side to deflect one of these pieces away from defensive duties. In the example shown to the left, White can play 1.Qxc6 and black cannot reply 1...Rxc6 because of 2.Rd8+ Rxd8 3.Rxd8# with a back-rank mate. Black therefore loses his bishop for no compensation—and Black has no good continuation because of the threat to chew up more material with Qxa8 or Qxc8, for example, 1...Qa6 2.Qxa8! Rxa8 3.Rd8+ Rxd8 4.Rxd8#. If Black tries to defend the back rank so that White's queen and bishop are skewered, White can keep an extra piece, for example 1...b5 (defending d8 with the queen) 2.Qf3! keeping the rook on c8 stuck to the defense of the rook on a8, or 1...g6 (creating luft) 2.Qf6! and Black still can't take due to the back-rank mate. Back-rank threats can be guarded against more permanently by moving one of the pawns in front of the king to give the king a ''flight square'' (or ''luft''). If it were Black to play in the example to the left, he could counter White's threat with, for example, 1...g6, giving the king a square on g7 to which it can safely move. Note, however, that 1...h6 in this example would not do the job, as after the d3-rook moves, the h7-square is covered by the white bishop. It is often not a good idea to play such pawn moves unless there is a pressing need to do so, as they can not only represent a loss of time, but may also allow enemy penetration around the squares weakened by the pawn advance. In many chess openings, however, they are often played for some other purpose, before any back-rank threat has emerged (...h6 is often played to "put the question" to a white bishop on g5, for example; see also Fianchetto). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Back-rank checkmate」の詳細全文を読む スポンサード リンク
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