# Back in time, in my time, all the time

I present to you all a highly interesting problem that I came across awhile ago on Tim Krabbe’s site.

It’s White move and win, i.e. reach a winning positon, in 21 moves.

David Gurgenidze & Velimir Kalandadze, Shakhmaty v SSSR 1975, 2nd Prize

You may only use your own brain power! Good luck!

Bonus: Explain the title in relation to the solution! ;D

• I think this might be a duplicate from a few years back... – Dr Xorile Sep 20 '19 at 20:42
• Are you sure it's 21 moves? Not 22? – Dr Xorile Sep 20 '19 at 21:24
• Technically, the starting position is already a winning position :) – Arnaud Mortier Sep 21 '19 at 9:04

I vaguely remember seeing this a few years ago so I had a head start on working it out again. Someone with better searching skills will have to see if it's a duplicate. It's a very clever puzzle.

The basic idea is to mate with a promoted knight on b7 or with the rook on a1. The challenge is that it's very easy to stalemate. Black's idea is that he can't move off the back rank unless it's check. But if it's check he can just keep checking because white cannot take the black rook without making it a stalemate.

So, here's the solution (it's 22 moves, so maybe I have something slightly wrong):

1. e8=N Rg1 (Other rook moves give 2. Nd6 and 3. Nb7# or Ra1# is unstoppable. The idea here is that RxP is a draw)
2. Kh5 Rf1 (or c,d,e here and below)
3. g5 Rg1 (Now we need to get a piece to g3 without allowing check. So the next moves are going to be promoting the pawn and then moving the queen back while shielding the king)
4. Kh6 Rf1
5. g6 Rg1
6. Kh7 Rf1
7. g7 Rg1
8. Kh8 Rf1
9. g8=Q Rg1
10. Qg7 Rf1
11. Kh7 Rg1
12. Qg6 Rf1
13. Kh6 Rg1
14. Qg5 Rf1
15. Kh5 Rg1
16. Qg4 Rf1
17. Kh4 Rg1
18. Qg3 Rd1 (The idea is that now the King can escape from the Rook checks)
19. Nd6 Rd4+
20. Kh3 Rh4+
21. Kg2 Rh7
22. Ra1#

Here's a gif (generated from https://www.chess.com/gifs):

Bonus question:

The title is from lyrics to an Eiffel 65 song. The next words are "Up and down", which is obviously the essence of the solution!

• Nice job (+1). I'd never have found it so fast so no regrets - plus it was really fun. – Arnaud Mortier Sep 20 '19 at 22:42
• Thanks. You too. I had the shape in my head but had to figure out the details. – Dr Xorile Sep 20 '19 at 22:58

Well, while @DrXorile found the answer, I'd figured out the key idea and the first couple of moves of the actual answer, but then my attempt is quite different. In the end, I understood why it doesn't quite work, but it still involves a really beautiful sequence and requires sharp play by Black. So here it is.

First thing, none of Black's pieces can move except the e1 rook, meaning that capturing this rook without check will result in stalemate.
This gives us Black's strategy to annoy us: keep checking our king with this unprotected rook, as we cannot capture it, until the 50-move rule applies. Essentially, we cannot allow Black to deliver check.

On the other hand, this black rook is not completely free: leaving the 1st rank would result in Ra1#. For instance, if White starts with a promotion, Black cannot capture the promoted piece immediately because of this threat.

Now to the point: the idea is 1. e8=N!! threatening a mate from a completely different angle: 2. Nd6 and 3. Nb7. Black's rook cannot deal with both mate threats.

to avoid 2. Nd6 and having to deal with two mate in 1 threats is 1. ... Rg1 threatening check (and therefore a draw). White answers with 2. Kh5, preventing any checks. The threats remain for Black: again, capturing the rook would make Nd6 Nb7 unavoidable, and leaving the first rank without check is instant death. Keep threatening check remains the only option.
Black answers with 2. ... Rc1 or any rook move not leaving the 1st rank and threatening check.
3. Nd6 Now both mate in 1 threats are in place, but check is coming. However, White is ready to take it as they have a secret plan. 3. ... Rc5+
4. Kh4 and for the next few moves Black has only one way to keep checking the white king, and absolutely needs to do it.
4. ... Rh5+ 5. Kg3 Rh3+ 6. Kf2 Rf3+ 7. Ke2

Now Black has essentially two options, and both lead to its fall for different reasons.

$$\bullet$$ Either black only checks the white king from the top or from the right, and in this case Black cannot stop White from reaching the b1 square, e.g.
7. ... Re3+ 8. Kd2 Re2+ 9. Kc1 Re1+ 10. Kc2 Re2+ 11. Kb1
or
7. ... Re3+ 8. Kd2 Rd3+ 9. Kc2 Rc3+ 10. Kb1

$$\bullet$$ Or black checks white from below at some point, e.g.
7. ... Re3+ 8. Kd2 Re2+ 9. Kc1 Re1+ 10. Kc2 Rc1+

Now

$$\bullet$$ If Black checks white from below, the idea is
11. Rxc1! You can capture the rook without stalemate as you set the pawn free by doing so, and the pawn promotion doesn't come with check.
11. ... h1=Q (not done yet as the queen covers both mating squares, b7 and a1!)
12. Nb7+ Qxb7 13. Ra1#
or
12. Ra1+ Qxb7 13. Nb7#.

$$\bullet$$On the other hand, if White reaches b1, then you have the magnificent sequence 11. ... Re1+ 12. Ka2 Ra1+ 13. Rxa1 h1=Q 14. Nb7+ Qxb7 15. Kb1#.

Now the reason why this sadly fails is that Black can ensure having their rook on the d file when Kb1 is played:
7. ... Re3+ 8. Kd2 Rd3+ 9. Kc1 Rd1+ 10. Kc2 Rd2+ 11. Kb1
and then instead of 11. ... Rd1+, Black will simply capture the knight as the other threat of Ra1# is temporarily blocked by the white king.

• You said: "2. ... Ra3 or any rook move not leaving the 1st rank and threatening check". Did you mean 2. ... Rc1? – Dr Xorile Sep 20 '19 at 22:57
• @DrXorile Oh! Yes, this is a typo. Thanks. – Arnaud Mortier Sep 20 '19 at 22:58