each player's pawns are free to advance to attack the opposing king's castled position without exposing the player's own castled king. Opposite castling is a common feature of many openings, such as the Yugoslav Attack. Tactics involving castling Tactical patterns involving castling are rare. One pattern involves castling queenside to deliver a : the king attacks a rook (on b2 for White or b7 for Black), while the rook attacks a second opposing piece (usually the king). In the example on the right, from the game Mattison–Millers, Königsberg 1926, Black played 13...Rxb2 and resigned after 14.0-0-0+, which wins the rook. Chess historian Edward Winter has proposed the name "Thornton castling trap" for this pattern, in reference to the earliest known example, Thornton–Boultbee, published in the Brooklyn Chess Chronicle in 1884. Other chess writers such as Gary Lane have since adopted this term. Another example of tactical castling is illustrated in the diagrammed position from the correspondence game Gurvich–Pampin, 1976. After 1.Qxd8+ Kxd8 2.0-0-0+ Ke7 3.Nxb5, White wins a rook by castling with check and simultaneously unpinning the knight. Such a double attack can also be made by castling kingside, though this is much rarer. In this position from the blindfold game , 2007, the move 19...0-0 threatens to win the h7-rook as well as indirectly threatens to deliver back-rank mate. Black will thus win the g5-knight next move; 20.Rh6 Bxg5 21.Rxg6+ Kh7 22.Rxg5 would not work, as it would be met by 22...Rf1. Examples Viktor Korchnoi, in his 1974 Candidates final match with Anatoly Karpov, asked the arbiter if castling was legal when the castling rook was under attack. The arbiter answered in the affirmative, Korchnoi executed the move, and Karpov resigned shortly after. Castling occurred three times in the game Wolfgang Heidenfeld–Nick Kerins, Dublin 1973. The third instance of castling, the second one by White, was illegal, as the white king had already moved. The game is as follows: 1.e4 e6 2.d4 d5 3.Be3 Nf6 4.e5 Nfd7 5.f4 c5 6.c3 Nc6 7.Nf3 Qb6 8.Qd2 c4 9.Be2 Na5 10.0-0 f5 11.Ng5 Be7 12.g4 Bxg5 13.fxg5 Nf8 14.gxf5 exf5 15.Bf3 Be6 16.Qg2 0-0-0 17.Na3 Ng6 18.Qd2 f4 19.Bf2 Bh3 20.Rfb1 Bf5 21.Nc2 h6 22.gxh6 Rxh6 23.Nb4 Qe6 24.Qe2 Ne7 25.b3 Qg6+ 26.Kf1 Bxb1 27.bxc4 dxc4 28.Qb2 Bd3+ 29.Ke1 Be4 30.Qe2 Bxf3 31.Qxf3 Rxh2 32.d5 Qf5 33.0-0-0 Rh3 34.Qe2 Rxc3+ 35.Kb2 Rh3 36.d6 Nec6 37.Nxc6 Nxc6 38.e6 Qe5+ 39.Qxe5 Nxe5 40.d7+ Nxd7