Monday, April 28, 2008

Plachutta intersection

How is related the Nowotny intersection with the Grimshaw intersection? There is a Grimshaw intersection, then we put on it a white piece, to force mutual black interferences, and we name this square Nowotny intersection.

Well, the Plachutta intersection is similarly related with the Wurzburg – Plachutta intersection.

Theme Plachutta intersection : The white moves a piece onto the intersection of two black linear pieces (with similar way of movement), that is on a Wurzburg – Plachutta intersection, to force mutual black interferences.

The theme Plachutta creates two simultaneous threats and needs at least three moves.

Let us see a simple presentation of this theme in problem-69, by Manolas: The Rook Re3 stops the checkmate Sa3#. The Queen Qd1 stops the checkmate Bd7#. The lines of action of the two black pieces intersect on square d3.

(Problem 69)
Manolas Emmanuel,
published in Award Manolas-60 JT, 12-07-2010
White plays and mates in 3 moves
#3 (7+8)

Tries: {1.Bd7+? Qxd7!}, {1.Sc3+? Rxc3!}, {1.Sa3+? Rxa3!}.
Key: 1.Sd3! [2.Sa3# / Bd7#]
The key is a Plachutta move. It gives a flight to the black king, sacrificing a rook.
1...Qxd3 2.Sa3+ Qxa3 3.Bd7#
1...Rxd3 2.Bd7+ Rxd7 3.Sa3#

The Bg7 may try to defend leaving square g7, then the Rook Rh7 guards d7, thus the Bishop must move to a square from which it can guard a3.
1...Bb2 2.Bd7+ Rxd7 3.Rc5#

The black Bishop corrects the arrival square, (this is called black correction), and guards a3 from another diagonal.
1...Bf8 2.Bd7+ Rxd7 3.Sc3#

The black King in rage starts capturing white pieces:
1...Kxc4 2.Be6+ and now
___2...Kb5 3.Bd7# (capturing the Rook, the King becomes target of the indirect battery Bishop-Rook, which was aiming at a square next to the King, not directly at the King).
___2...Kxd3 (another black correction, the hyper-active King has captured two pieces, but...) 3.Bc4#

The outstanding German composer Rehm, who is a specialist on more-movers, shows in his Problem-70 the theme Plachutta, twice!

(Problem 70)
Hans-Peter Rehm,
Fifth Prize, ”Deutsche Schachzeitung“, 1963
White plays and mates in 5 moves
#5 (8+9)

Tries: {1.Bb6+? Sxb6!}, {1.Bc7? Sxc7!}, {1.Be7? Rc1!}, {1.Sf5+? Kxd3!}, {1.Sc2+? Rxc2!}.
Key: 1.Bg5! (with threat a Plachutta move 2.Se2 and double threat 3.Bxe3# / Sc2#, resulting in
2...Ree2 3.Sc2+ and 4.Bxe3#
or 2...Rhe2 3.Bxe3 and 4.Sc2#)

The black passes Rh2 over the critical square e2 and takes care not to play 1...Rd2?? (bad move with continuation 2.Bxe3 Rxe3 3.Sf5 and 4.Rxe3#).
2.Be7 Rc1
The black defends as he did in one of the tries. But now the stage is ready for the second Plachutta on square c2.
and 3...Rcxc2 4.Se2+ Rxe2 5.Bc5#
or 3...Rbxc2 4.Bc5+ Rxc5 5.Se2#

[This post in Greek language].

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