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mrmip

Joined: 05 Nov 2005
Posts: 230
Location: Finland

 Posted: Wed Oct 15, 2014 5:09 am    Post subject: Line Themes Line themes involve line moving (=Q,R,B) pieces and one or more thematic lines (=files, ranks or diagonals). Line themes can be further divided into two groups: - Line utilizing themes that involve clearance and doubling operations. These are predominantly white themes, i.e. white will make his position stronger by these operations. - Line interference themes. These are invariably black themes that involve lack of coordination with black forces. We have already introduced basic 2-move Grimshaw and Novotny themes (Puzzle #1532) as well as simple two-move Bristol line-clearance theme (Puzzle #1538). To sum up these basics: * Novotny is a black theme, where white puts a unit on the square, where the lines of two differently moving line pieces (normally R and B) cross. Black then captures the white unit on this critical square with one of the line pieces,causing a fatal block to the other line piece. * Grimshaw is exactly the same theme, but without the white sacrifice on the critical square. White uses some other threat to cause the self-interference of the black line pieces. * Bristol is a white line clearance theme. A pair of similarly moving line pieces stands on a thematic line forming a battery. The critical square (Mating square) stands somewhere further down the line. The front piece of the battery moves along the line beyond the critical square and then the way is clear for the rear piece to move to mating square, supported by the front piece. [- end of summing up basics-] Now let us turn to three- or moremover line themes. We will start with black (interference) themes. (1) Critical Novotny and critical Grimshaw work exactly as the equivalent simple themes above. Only there is a preliminary threat(s) from white that causes one or both black pieces move over the critical square before the thematic interference. Remember that these themes concern differently moving pieces on crossing lines. (2) Plachutta is a theme based on the interference of the similarly moving pieces on crossing lines. White puts a unit on the critical square, causing one of the black line pieces to capture it. Then white utilizes the fact that this piece is now overloaded as it watches over both thematic lines. It is next forced forward along the mutual line of the black pieces and a catastrophe will happen on its now unguarded original line. (3) Holzhausen theme holds the same relation to Plachutta as Grimshaw holds to Novotny. The interference is caused without need to sacrifice on the critical square. Sometimes Holzhausen is called Wurtzburg-Plachutta. (4) There is also an interference theme when a pair of similarly moving pieces interferes with each other on the same line. This theme is called Anti-Bristol, because here black pieces make each other weaker, while in proper Bristol a pair of white pieces makes themselves stronger. Next a few white themes. The first three are closely related themes for similarly moving pieces on a thematic line. They differ on the way they form and utilize a battery on that line. (5) In the Turton doubling one of the pieces already on the thematic line moves 'backwards' (= away from the critical square) to make room for adding the front piece of the battery, that later mates by moving to the critical square. (6) The Zepler doubling is similar to the above, but here the front piece, already on thematic line, moves forward (= towards the critical square) making room for the supporting rear piece to form the battery. (7) In the Bristol clearance the front piece moves over the critical square to support later the rear piece's move to the critical square. So the front piece clears the line for the rear piece movement. This clearance move can (and often does) happen before the actual battery is formed, ie. anticipating the battery. I consider 'proper' Bristol to include the building of the battery, so that it is 3- or moremover theme. To highlight the differences between the three themes above, I composed a game like puzzle that has 3 solutions. One of each type discussed. Mate in 3. Three solutions. Composed by mrmip, 2007 Thematic line is b1-h7. Critical square is g6. Here are the solutions: 1.Bb1{going back on the thematic line} Rd7 2.Qc2 {Battery} Be5 3.Qg6# {Theme=Turton doubling} 1.Qe2{establishing front piece} Rd7 2.Qe4 {Battery} Be5 3.Qg6# {Theme=Zepler doubling} 1.Qb1{Forming the battery} Rd7 2.Bh7 {Moving beyond critical square} Be5 3.Qg6# {Theme=Bristol clearance} There are a couple of other themes involving differently moving pieces on the same, thematic line. (8 ) The Indian theme. Here a front piece will mask the influence of the rear piece along the thematic line, in order to relieve a stalemate position. Then, after a black move, the line is unmasked with fatal consequences. (9) The Annihilation theme. Here white moves a line piece along the thematic line so that black can (and usually is compelled to) capture it. Next the black capturer will vacate the line and another white line piece utilizes the thematic line by moving beyond the capture square and mating. The tutorial puzzles #1646-#1660 present the above line themes (in no particular order)._________________There are only three kinds of chessplayers - those who can count and those who cannot....
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