Rook and Knight Perpetual Checks
Let me tell you how I almost changed chess history: the other day I was watching Andrew Martin’s DVD on the Benko Gambit. In the DVD Martin shows the classic game Taimanov-Bronstein, 1953 where Bronstein used the Benko gambit to create a true masterpiece. I had seen the game before but got carried away by its charm and watched it again. At some point, the game arrived at the following diagram:
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After 1…Na4! (here the knight on the side of the board proves pretty useful) 2 Rc8 Nxc3 3 Rxc4 Nd5 Black won easily because the threats on f4 and g2 soon win a second pawn. This looks pretty straight forward but when I replayed the game I noticed that after 1… Na4!?? White can actually draw the game immediately with 2 Rf8+! Kg7 3 Ne6+ Kh7 4 Rf7+ Kg8 5 Rf8+ and so on... Could that be? Did I find a hole in a classic masterpiece of Bronstein? I played it again and again and could not see where I went wrong so I must have been right – White’s rook and knight give a perpetual check!
To tell a long story short I did not change chess history because the position shown by Martin was not the one that really happened in the game. In the real Taimanov-Bronstein game the black king stood on f7 and not on f6, a fact that makes the perpetual check impossible after 1…Na4. This was a bit disappointing but still I thought I found a neat perpetual pattern with a knight on the sixth. Is this pattern seen elsewhere in master level games? Well, the pattern appears and it is also quite useful to know.
In this position, taken from Kofidis – J. Howell, Groningen 1983, White is not in a very pleasant position. The queen is attacked and if it retreats Black gets a dangerous initiative, For example 1 Qd1 hxg4 2 fxg4 Nf4! 3 gxf5 Rxg2+ 4 Kh1 Qc6 and Black wins. Still, White, knowing the pattern of perpetual check, played 1 Ne6! and survived. If Black takes the knight then Qh6 wins, hence 1 Ne6! Rxd2 2 Rxf8+ Kh7 3 Rf7+ Kh8 (if 3…Kh6?? then 4 g5#) with a draw.
An even more remarkable save happened in the following diagram, taken from Votava – Wiedner, Vienna 1994.
Here it is not fully clear how Black can realize his material advantage but with the following mistake he gives White an immediate draw. Black played 1…Nxa2? (Instead of the correct 1…Qb6 defending e6) and a draw was agreed after 2 Nxe6+ Kh6 3 Rf8! (even with the h6 square at his disposal Black cannot avoid the perpetual because 4 Rh8# is now threatened) 3… Kh7 (3…g5 4 hxg5+ Kg6 5 Rf6+ is again… a perpetual) 4 Rf7+ Kg8 ½ - ½
We will finish with a grandmaster game as an exercise.
Here (Kovacevic-Morovic, Pula 2000) White has just played Rg7-h7?, instead of Ba7 that would keep some winning chances. Black used the pattern we are discussing today to take an easy draw. How was it done (cover all possible routes of the white king).
Solution:
1… Rf1+ 2 Kh2 Rf2+ 3 Kh3 Rf1! (threatening Rh1#) 4 Kh2 (4 g4?! hxg4+ and Black has, at least, a draw by perpetual) Rf2+ ½ - ½