Tuesday, May 06, 2008

Themes Hamburg and Dresden

We continue presenting problems of the three relevant themes: theme Roman, theme Hamburg, theme Dresden. These themes contain the following common elements:

(a) The problems have at least one try.
(b) There is a General plan (German : Hauptplan), which becomes obvious with the moves after the try (the virtual play), but is not successful.
(c) A Pre-plan (German : Vorplan) is applied, which starts with the key and continues with modification of the defensive moves. Then the general plan reappears and is finally applied.
(d) The themes require at least 3 moves.

Theme Hamburg : The move of a black piece changes the way of defense of another piece.

(Problem 77)
Siegfried Brehmer,
Second Prize, ”German Ring Tourney”, 1948
White plays and mates in 3 moves
#3 (8+8)

First we see some tries with checking moves:
Tries: {1.Sb8+? Kc7!}, {1.Rd6+? Kxd6!}, {1.Rb6+? Kxd5!}, {1.Rbc5+? Kb7!}.

Next we see two tries relevant with the theme, (thematic tries):
Tries: {1.Sc4? [2.Rd6+] Rg6!}, {1.Rd4? [2.Rb6+] Rg5!}

Key: 1.f4! [2.Rb6 Kxd5 3.Sc7#].
If the pawn f7 moves, the Rook Rg7 will guard c7 (but then, the defensive moves of the Rook will be modified):
1...f6 2.Sc4 (and there is not the defense Rg6) Rd7 3.Rdc5#
1...f5 2.Rd4 (and there is not the defense Rg5) Rb7 3.Rbc5#
And another variation with en-passant capture of a pawn:
1...exf3 e.p. 2.e4 (holds Rd5) ~ 3.Rb6#

The Rook Rg7 has adequate defenses for the thematic tries with moves on file-g, but the pawn f7 changes the way of defense of the Rook, forcing it to move on row-7. When the Rook makes its defensive moves there blocks flights of the black King.

And now let us see the third theme of the group Roman - Hamburg - Dresden.

Theme Dresden : The move of a black piece changes the (good) defense of piece-A to (inadequate) defense of piece-B.

(Problem 78)
Erich-Ernest Zepler,
Fourth Prize, ”Dresdener Anzeiger“, 1927
White plays and mates in 3 moves
#3 (3+12)

There are several tries: {1.Rxa7+? Kxa7!}, {1.Rb6? Sc8!}, {1.Qxf5? Rxf5!}, {1.Qxc3? Bxc3!}, {1.Qe2? Ra4!}.

Another two tries relevant with the theme: {1.Qg2? [2.Qg8#] Rg4!}, {1.Qa2? [2.Rxa7#] Ra4!}.

Key: 1.Qf2! [2.Qg1 [3.Qg8#]].
The Rook Rd4 can not move because of Qxa7#.
1...f4 (if white plays 2.Qg1, black will continue with 2...Rg5)
2.Qg2 (not 2.Qa2? Ra4!) Rg5 3.Qxc6#
1...b4 (if white plays 2.Qg1, black will continue with 2...Rb5 and 3...Rb8)
2.Qa2 (not 2.Qg2? Rg4!) Ra5 3.Qg8#

In the virtual play the Rook Rc4 has adequate defense.
The moves of the pawns f5-f4 or b5-b4 change the 'defenses with Rc4' to 'defenses with Rc5', which are unable to stop the mate because they open the diagonals passing from c5.

[This post in Greek language].


trandism said...

There is a typo in the 4th try of the hamburg theme problem. It should be 1.Rbc5+

alkinoos said...

Thank you. It is corrected now.