# The Russian machine has a flaw

The year is 1969.

You, Robert James Fischer, are invited in a secret Russian basement to 'play a chess game against a strong opponent'. When you finally meet your opponent, a Russian bald guy who is more than twice as high than you, you quickly realize something : his brain has been modified by Russian scientists.

Intrigued, you show him a piece of paper on which a chess puzzle is printed : it took you 2 weeks to solve it, but the Russian guy instantly grabs it and violently tries to play the correct move on the piece of paper. It looks like he has some sort of chess computer attached to his brain.

Just before the game starts, he tells you, with a comically exagerated russian accent : "You play white. I will let you win. But you lose if you checkmate after move 40".

You are easily dominated. Before your 37th move, the position is the following :

This Russian dude is so good, he managed to place his pawns in illegal positions!

You instantly see how to checkmate in 5 moves. But... that would deliver checkmate on move 41, and you would lose the game. The Russian player has a smirk on his face - he thinks you cannot win in less than 5 moves, because he calculated all the possible outcomes.

Prove him wrong and checkmate black in 4 moves or less.

Tim Krabbe's castling (which was technically legal until 1972, and the game was set in 1969).

The moves are

1. d6+ Kh2 2. dxe7 Qh6 (or 2... h6) 3. e8=R and 4. 0-0-0-0# (placing white king to e3 and white rook from e8 to e2).

Note:

Until 1972, there was no requirement that the king and rook must be on the same rank when castling. So, technically a king could castle vertically along the e-file with a pawn promoted to rook on e8 (e1), because the newly promoted rook has obviously not yet moved!

• That was fast ! As a small addition to your answer, black should play h6 on move 2. If they play Qh6 white can just play Kd2 Rh1#, but if they play h6 then you must 'castle' because Kd2 would stalemate. Apr 7, 2020 at 11:00
• @classicalMpk Thanks! By the way, I'm in fact Russian. Apr 7, 2020 at 12:04

Maybe Robert James is playing

the Fischer random chess variant?

In that case...

... assuming we still have castling rights as white...

... we can mate in...

three moves:

1. d6+ Kh2 (Kg1 Ke2+ Kh2 Rh1#)
2. 0-0-0

with Rh1# following next regardless of what black does.

• Unfortunately here we are playing a normal chess game, but your answer is very creative and deserves my vote. Apr 7, 2020 at 10:54
• However, unfortunately this was not invented until 1990s. +1 nevertheless. Apr 7, 2020 at 10:55
• P.S. What after 1. P-Q6ch K-R7 2. 0-0-0 P-Kt7 (due to pawn on Q6, black Kt6 pawn is not pinned anymore)? (Using descriptive notation as a spoiler, since rot13 will not work good in this case.) Apr 7, 2020 at 11:13
• @trolley813 Hmm yeah, that's a good point. This doesn't work after all.
– Jafe
Apr 7, 2020 at 11:16