Tuesday, January 17, 2006
Single Line Interference
White to Move
Interference seems much less common than other types of tactics. In the Polgar brick I noticed that when I find interference it usually is when one piece moves onto an intersection line of 2 defenders, simultaneously blocking both lines and making recapture a problem either way (624/5334 for example). I don't know if anyone calls this double line or multiple line interference, but that seems to be a logical term for it.
This tactic has been difficult for me to spot in games, as I expect it is for many beginning and intermediate players. Repeatedly working through examples may be adequate preparation to spot it more regularly in-game, but I wanted to form a better understanding of it. I played around with it, composing some easy examples, breaking it down into simpler parts. This led me to think single line interference was a better starting place than double line interference. It still is messy! I made a less obvious, more complicated example (above). I hope this example shows that just blocking 1 line alone is enough to throw one out of typical move considerations into unnatural but strong sacrifice moves.
Answer: 1.Qd5! Threatening the smothered mate with 2. Nf7#
(1.Nf7+ is more of a mess as in Bxf7 2.gxf7 Nd7 3.Ng6+ Kh7 4.Qxe4 Kh6 5.Bc1+ Bf4 6.Bxf4+ Kh7 7.Nf8+ Kh8 8.Qh7#)
1...Bxd5 A peculiar result of 1.Qd5! is that Black's Rook and c6 pawn can't occupy the d5 square without creating a f7 vulnerability.
2.Rxd5 Threatening again the smothered mate with 3. Nf7#
2...Nd6 Defending f7 at all costs
(2...Rf8 leads to a quicker mate with the clearance move 3.Nf7+ Rxf7 4.Rh5#)
3.Bxd6 this is the fastest way to get rid of the defender and also keep the Rh5# idea going, which is pretty much now unstoppable
3...Rf8 averting mate for just another move
4.Nf7+ Rxf7 5.Rh5#
[White "New game"]
[Black "Fritz 8"]
[FEN "1n1r3k/1nb1N1p1/1pp3P1/6N1/3Qp2P/Bb6/5P2/3R3K w - - 0 1"]
1. Qd5 (1. Nf7+ Bxf7 2. gxf7 Nd7 3. Ng6+ Kh7 4. Qxe4 Kh6 5. Bc1+ Bf4 6. Bxf4+
Kh7 7. Nf8+ Kh8 8. Qh7#) 1... Bxd5 2. Rxd5 Nd6 (2... Rf8 3. Nf7+ Rxf7 4. Rh5#)
3. Bxd6 Rf8 4. Nf7+ Rxf7 5. Rh5# 1-0
Working on this helped me clarify a detail that I never saw fully discussed in any chess book: outnumbering the long-range pieces on a line and perpendicular. Thinking this way, Black could have stopped the Qd5 interference idea by having one more diagonal protector either along the a2-g8 diagonal or a8-h1 diagonal.
I suppose this kind of outnumbering rarely comes up, as it's extremely unlikely to have more than a Queen and Bishop on a diagonal. Another limiting thing for the defender is the difficulty of using pawns; obviously that only works if the square it's protecting is exactly 1 "forward" diagonal square away. Suffice it to say the attacker has a huge advantage, as he can throw pieces onto the interference square from any direction.
I am still reading the McDonald book incrementally, and I think it's helping. The continuity of moves and plans he describes continues to impress me. In "Game Two" though, his analysis of 28... f6 seemed a little weak, and Fritz confirmed it (thanks PMD for the file). It just shows that Masters are human, as I think he fell out of a vigilant doubting approach and simply argued for Black's move choice.
Back to solving problems. TCT Circle 4's days are numbered...
|Circle 1||Circle 2||Circle 3||Circle 4|
You usually see it in composed problems. I would put it low on my list of themes to practice for practical use- but very high on the aesthetics list.
I be curious to know if there was some kind of collection of interference themes that have appeared in actual tournament games.