BCPS

In Part 1, I showed you a problem by Mansfield which was what’s called a ‘complete block’ – there’s a mate set up for every black move if Black moves first. More common are problems in which there isn’t a mate already set for every black move, and in that case you need to find a ‘threat’ – a white first move that threatens a mate if Black were not to reply. Here’s one:

White to play and mate in two moves

This time you’ve learnt that the checks are unlikely to solve it! (Although just occasionally a composer will make a two-mover that does have a checking solution – it keeps skilled solvers on their toes!) It’s not a complete block, not least because Black has lots of neutral moves with his rook or bishop. So what could the threat be? What about 1.Rba1, intending 2.Ra5? Black has 1...c5!. 1.Ra4 perhaps, intending 2.Qb4 or 2.Bc2? Looks too crude, and indeed black has the defence 1...Rg4. So it has to be a queen move? Try them. Unfortunately, there are quite a few, but you work through them and after several false dawns you finally realise none of them work. The solution is instead the extraordinary 1.Kd6! which allows Black two checks. Both are met by unexpected cross-checks, which work because black’s rook, in giving the checks, has blocked the bishop from capturing the rook on b1.

Really hard for a problem newcomer to solve. Not too tough for a regular solver, however, because in problems the kings very often move – composers often like to have the white king playing a big role in the solution. I think that a top solving-grandmaster would take less than 15 seconds to solve this one! He’d see the interferences between the rook and the bishop, and immediately try 1.Kd6. For the rest of us, it’s a tough nut. Notice that white’s key move grants the black king two moves, whereas in the diagram it didn’t have any – the opposite of that (where the key move reduces the number of ‘flight squares’ the black king has) is very rare in problems, being considered a crude key. So a flight-taking key move is very unlikely to be a solution to a problem.

Gerry Anderson (not the one who wrote ‘Thunderbirds’!) composed this and it was first published in ‘Il Secolo’ in 1919. In the total trivia department, he was the last person to play chess against Alekhine.

(This and the other parts of this series were first published in The British Correspondence Chess Association magazine ‘Correspondence Chess’ in 2010. The BCCA site is www.bcca.info)