Has this ever happened to you? Your opponent makes an illegal move, for some reason you don’t notice that it’s illegal, and instead of stopping the clock to sort things out, you play a normal move and the game continues. This happened to me twice last season. What interested me most was the accompanying thought processes. In both cases the illegal move left me dumbfounded and thinking something like this: “I completely overlooked this move. I had no idea he / she could play that. What do I do now?”
What happens here is that when you look at a position, and consider what your opponent might do, your mind automatically filters out illegal moves. Not just the obvious ones like moving the king four squares instead of one, but anything that contravenes the laws of chess. So when your opponent then makes an illegal move, you’re totally unprepared for it.
Position 1 – Opponent A v Rodney Barking
Black to move. I am totally winning this position. I am about to queen with check. I wandered off to find a spare black queen, which had the effect of breaking my concentration. On returning I played 39…c1=Q+ and sat back waiting for my opponent to resign. After some thought my opponent ignored the check and responded with a totally unexpected counter-attacking move, 40.hxg6, opening up my kingside defences. I was so shaken by this that you could have knocked me sideways. How best to defend my king? I played 40…Qh6.
My opponent then became very agitated and started moving pieces around the board in a random fashion. I asked if this was a resignation. No response. I asked again. No response. So I stopped the clock, believing the game to be over, and reset the board in the starting position, before noting a black win on the match result sheet. Only later did I discover that my opponent was deaf and could not hear what I was saying. My opponent was agitated on seeing the illegal move and was trying to correct it. I raised this with the opposition captain, expecting a challenge to the result of the game, but the captain let it stand. Apparently my opponent had done this in another game earlier in the season and everyone found it rather embarrassing.
Position 2 – Rodney Barking v Opponent B
This is a Caro-Kann Advance Variation where I have sacrificed a pawn in order to immobilise my opponent’s kingside. The immediate threat is to capture the bishop on f8. Black doesn’t have a good reply. 15…Nf6 and 15…Qe8 both lose material, so Black has to move the king to d7 or c7 when I can win in straightforward fashion by rapidly opening the queenside. So I was completely surprised when my opponent castled into safety with 15…0-0-0. My attack had disappeared. I developed my queenside, and won the game eventually, although a better plan would have been to double rooks on the f-file, forcing …Qe8 to defend the bishop, allowing me to capture the pawn on e6 and open up the centre. I did not see the illegal move until I inputted the moves on the computer later, and when I reached 15…0-0-0 the computer refused to move and just sat there and stared at me.
How do you stop this sort of thing happening in future? When your opponent makes a completely unexpected move, don’t just accept it and plan your response, but take a moment to look at the position afresh and work out why you didn’t see it. Then you can stop the clock and claim an extra two minutes for the illegal move.