Fortress (chess)
A fortress in chess is a position in which one party holds so stationed their stones by trains wait and see, that the counterparty will not penetrate to the king of the defending side can still force a settlement in a won endgame. With the help of a fortress, a material losing party reach a draw.
The Russian chess coach Mark Dworezki defines a stronghold as an " impregnable position in which one restricts oneself to passive defense." Occasionally, possibly an exact train was necessary. The fortress was an important method of defense in the final.
Examples
In this example, Black does have a material advantage of a tower against two pawns, but he can not win because his king can not intervene and white checked the burglar fields of the tower on the h-file.
1 ... Th8 - h3 2 K g1 - g2! Th3 - h6 3 K g2 - g1! draw, because the black king is reliably shielded from the two white farmers, and the tower alone can not penetrate.
In this position from a lot Arshak Petrosian - Laszlo Hazai Black is at loss. White has the simple maneuver Db2 -d2, Ka2 -b3, c3 Sa4, Kb3 -a4, Sc3 -a2 -c1 -b3, after which White would conquer the Ba5 and then easily wins. Hazai found the witty train 1 ... Da7 - b6? , Which still represented a last case, fell into the Petrosian. He banged 2.Sa4xb6 ? the lady, because he believed he could avoid by the h5- h4 threatening fortress with the pawn sacrifice 3.h3 - h4 after 2 ... c7xb6. However, after 3 ... g5xh4 Black sacrificed the following train in turn the farmers with 4 ... h4 - h3, and h5- h4 5.g2xh3 after each burglary possibility was blocked.
Other examples are:
- Following the famous combination in the game Tylkowski - Wojciechowski, Poznań 1931 White had possibly lose only because he failed to establish starting with 37.Tb3 a fortress.
- See also: The wrong runners
Frequent fortresses
In diagram 1 White commutes with the tower just between f3 and h3, and with the king between g1, h1 and h2. The black king can not in any case exceed the 3rd row. If the king would stand on e2 instead of e4, he could never exceed the f-file.
In Diagram 2 Black can enter with the king never permanent the fields f1, f2, f3, g3, h3. If the white king is forced to g1 or h2, the runner between h1 and g2 can commute.
In Diagram 3 White commutes easy with the king between g1 and h1. If the black runner poses on f3, this may only be beaten if the white king is on g1, because white makes the opposition after Kxf3 by train Kf1 and holds a draw.
Active fortresses
In most cases, there is a fortress from a small area of the chessboard, which is held by the weaker side, or the stronger side is not able to break through a farmer's Wall. Surprisingly, however can build fortresses also acting aggressively figures.
The black king is trapped and completely unable to move. Without him, the lady can not checkmate, and to sacrifice for a knight, leads to an inconclusive ending. The only possible gain attempt would be that black with the lady in turn locks up the white king, white brings in a tight spot and the jumpers have to part with loss. But this would only be on the fields f7 or g6, which controls both the Springer e5. Therefore, the position is a draw.
Problems for chess computers and chess programs
Since fortresses do not represent a definitive end game (such as deadlock ) and one side is permanently superior material, chess computers and chess programs a fortress are usually not recognized as such in a position with their normal valuation methods. Such skills must be programmed separately into it.
After 1 De7xc7 Kb7xc7 2 b2- b4! White has built a fortress. Whether Black exchanges on b4, c4 by the farmers to advance or let him stand on c5, does not matter - the black farmers are not on the white king over, and its black counterpart is locked out by the white farmers. Shredder 7.04 was in 2003 not able to recognize this position as a simple draw.