# Longest sequence of unique series moves

Clearly a spawnoff of the preceding question, but far easier to analyze, and maybe helping a bit to solve that one too.

Take the starting position, remove all black pieces to simplify and now make only white moves. Again, if you can reach the position in fewer moves or the same number of moves in a different way, the game stops and your score is the number of moves.

Example: 1.a3. You now only have 2.Ra2 and then you are stuck. I would be impressed if anyone even reaches 10 moves.

Jacobi can help with this.

Addendum 10/29/2022: See @Evargalo's answer below, in which they have concocted a verified, again by Jacobi, 30 move sequence.

Silly Hauke, did you not check the PDB database: "k='series' and stip='bp'"? :-)

I found a seriesmover that can be withered down to 24 moves to fit the bill.

#1

``````[Title "François Labelle, Phénix 279-280, Series Proof Game In 31.0 Moves, Abridged To 24.0"]
[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w KQ - 0 1"]

1. Nc3 null 2. Nd5 null 3. c3 null 4. Qa4 null 5. Qa6 null 6. a4 null 7. a5 null 8. Ra4 null 9. Rg4 null 10. Rg5 null 11. g4 null 12. Bg2 null 13. Be4 null 14. Bb1 null 15. d3 null 16. Bf4 null 17. e3 null 18. Ne2 null 19. Rg1 null 20. Rg3 null 21. Rh3 null 22. Rh6 null 23. h3 null 24. Bh2
``````

I computer verified this with Jacobi, as linked above by @Hauke Reddmann, using this string:

EnglishN forsyth 8/8/8/8/8/8/PPPPPPPP/RNBQKBNR stipulation ser-a=>b24 forsyth 8/8/Q6R/P2N2R1/6P1/2PPP2P/1P2NP1B/1B2K3

It can be extended to 29 with a different move order, starting at move 24 .@Evargalo I ran Jacobi with this code: EnglishN forsyth 8/8/8/8/8/8/PPPPPPPP/RNBQKBNR stipulation ser-a=>b29.0 forsyth 8/8/Q6R/P2N2R1/5PPK/2PPP1NP/1P5B/1B6

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w KQ - 0 1"]

1. Nc3 null 2. Nd5 null 3. c3 null 4. Qa4 null 5. Qa6 null 6. a4 null 7. a5 null 8. Ra4 null 9. Rg4 null 10. Rg5 null 11. g4 null 12. Bg2 null 13. Be4 null 14. Bb1 null 15. d3 null 16. Bf4 null 17. e3 null 18. Ne2 null 19. Rg1 null 20. Rg3 null 21. Rh3 null 22. Rh6 null 23. h3 null 24. Bh2 null 25. f4 null 26. Kf2 null 27. Kg3 null 28. Kh4 null 29. Ng3
``````
• Silly Hauke should have considered MPF in the first place, of all things :-) Oct 25, 2022 at 7:31
• Those beautiful constructions feel like Jeu de taquin en.wikipedia.org/wiki/Jeu_de_taquin Oct 25, 2022 at 8:10
• I think there is a mistake in the problem by François Labelle because 25.Nf6 instead of 25.Ndf4 works just as well (and could have been played earlier). It would make much more sense if the solution included 26. Ng2 instead of 26.Nh5. Oct 25, 2022 at 8:13
• @Evargalo: Discussed on MPF (inclusive the fact that Ng2 won't work). Nf6 checks a Ke8 (it seems that black pieces present are implied; the FEN on PDB contains them). Oct 25, 2022 at 16:55
• I think the 29 moves version is cooked because of 1.e3, 3.Qa6, 5.a5, 8.Rg5, 10.Nd5, 11.c3, 13.Bd3, 14.Ne2, 15-18.Rg1-g3-h3-h6, 19.f4, 22.Kh4,23.h3,24.d3,25-28.Bd2-e1-g3-h2,29.Ng3 Oct 26, 2022 at 11:22

My current best try is 33 moves.

(a previous attempt in 34 moves has been demolished by my friend Yosha Iglesias)

The most promising idea I have found is to promote a pawn into a bishop and bring it back to the 2d or 1st rank.

The record (33 moves) is reached with the b-pawn :

Series shortest proof game - 33, White pieces only (C?) :

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. b4 null 2. b5 null 3. b6 null 4. b7 null 5. b8=B null 6. Be5 null 7. Beb2 null 8. c3 null 9. Qa4 null 10. Qa6 null 11. a4 null 12. a5 null 13. Ra4 null 14. Rf4 null 15. Rf6 null 16. f4 null 17. Kf2 null 18. Kg3 null 19. Kh4 null 20. g3 null 21. Bh3 null 22. Be6 null 23. h3 null 24. Rh2 null 25. Rf2 null 26. Rf3 null 27. Rd3 null 28. Rd8 null 29. d3 null 30. Nd2 null 31. Nb3 null 32. Bd2 null 33. Nc1
``````

The longest version that has been checked with Jacobi (in 21217 seconds!) is 32 moves long:

Series shortest proof game - 32, White pieces only (C+) :

1.b4 2.b5 3.b6 4.b7 5.b8=B 6.Be5 7.Beb2 8.c3 9.Qa4 10.Qa7 11.a4 12.a5 13.Ra4 14.Rf4 15.Rf5 16.f4 17.Kf2 18.Kg3 19.Kh4 20.g3 21.Bh3 22.Bg4 23.h3 24.Rh2 25.Rf2 26.Rf3 27.Rd3 28.Rdd5 29.d4 30.Sd2 31.Sf1 32.Bd2

Previous record was 30 moves with the a-pawn, also verified by engine thanks to Rewan Demontay.

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. a4 null 2.a5 null 3.a6 null 4.a7 null 5.a8=B null 6.Bd5 null 7.Ba2 null 8.b3 null 9.Bb2 null 10.Bf6 null 11.Nc3 null 12.Rb1 null 13.Rb2 null 14.Qa1 null 15.Bb1 null 16.Qa4 null 17.Qh4 null 18.g4 null 19.Bg2 null 20.Bb7 null 21.Nf3 null 22.O-O null 23.Kg2 null 24.Kg3 null 25.Kf4 null 26.Ke5 null 27.Kd6 null 28.Kc7 null 29.Kb8 null 30.Ka8
``````

The a-pawn is so strong that we can even get to 25 moves by playing only the queenside:

Series shortest proof game, White pieces only, 25 moves :

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. a4 null 2.a5 null 3.a6 null 4.a7 null 5.a8=B null 6.Bd5 null 7.Ra8 null 8.Ba2 null 9.b3 null 10.Ba3 null 11.Be7 null 12.Na3 null 13.Qa1 null 14.Kd1 null 15.Kc1 null 16.Kb2 null 17.Kc3 null 18.Kd4 null 19.Ke5 null 20.Kf6 null 21.Kg7 null 22.Kh8 null 23.Qg7 null 24.Bf6 null 25.Qb7
``````

With a bishop pawn (c- or f-), there are many ways to reach 28 moves :

1.f4 2.f5 3.f6 4.f7 5.f8=B 6.Bc5 7.Bf2 8.e3 9.Ke2 10.Kd3 11.Kc4 12.Kb5 13.Ka6 14.Bb5 15.Se2 16.Rf1 17.Bg1 18.Rf4 19.Rb4 20.c4 21.Qa4 22.b3 23.Bb2 24.Be5 25.Sbc3 26.Re1 27.Sc1 28.Re2 (C+)

1.f4 2.f5 3.f6 4.f7 5.f8=B 6.Bc5 7.Bf2 8.e3 9.Bd3 10.Se2 11.Rf1 12.Bg1 13.Rf4 14.Ra4 15.c4 16.Qb3 17.Qb8 18.b3 19.Bb2 20.Bh8 21.Sbc3 22.O-O-O 23.Bb1 24.Kc2 25.Kd3 26.Kd4 27.d3 28.Rd2 (C+)

1.c4 2.c5 3.c6 4.c7 5.c8=B 6.Bf5 7.Bc2 8.d3 9.Be3 10.Sd2 11.Rc1 12.Bb1 13.Rc4 14.Rg4 15.f4 16.Kf2 17.Kg3 18.Kh4 19.Kh5 20.h4 21.Rh3 22.Rhg3 23.Sh3 24.Bg1 25.e3 26.Be2 27.Bf3 28.Qe2 (C+)

Here is 28 moves with the g-pawn :

1.g4 2.g5 3.g6 4.g7 5.g8=B 6.Bd5 7.Bdg2 8.Sf3 9.Rg1 10.Bh1 11.Rg4 12.Rc4 13.d4 14.Kd2 15.Kc3 16.Kb4 17.c3 18.Qa4 19.Qa8 20.a4 21.a5 22.a6 23.a7 24.Ra6 25.Ka5 26.b4 27.Bb2 28.Ba1 (C+)

With the h-pawn, I also get 28 moves :

1.h4 2.h5 3.h6 4.h7 5.h8=B 6.Be5 7.Rh8 8.Bh2 9.f4 10.Kf2 11.Kg3 12.Kh4 13.g3 14.Bh3 15.Be6 16.Sh3 17.Qg1 18.Qa7 19.d4 20.Be3 21.Sd2 22.Rf1 23.Rf3 24.Bf2 25.Rb3 26.Rb5 27.b4 28.Sb3 (C+)

Alternative finish: 1.h4 2.h5 3.h6 4.h7 5.h8=B 6.Be5 7.Rh8 8.Bh2 9.f4 10.Kf2 11.Kg3 12.Kh4 13.g3 14.Bg2 15.Be4 16.Sf3 17.Qg1 18.Qc5 19.d4 20.Bd2 21.Bb4 22.Sc3 23.Rd1 24.Rd3 25.Sd1 26.Ra3 27.Ra4 28.Ba3 (C+)

Finally, the central pawns are not very promising unless I miss some smart trick...

Without pawn promotion, this construction is in 22 moves :

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. Nc3 null 2.Ne4 null 3.c3 null 4.Qa4 null 5.Qa8 null 6.a4 null 7.Ra3 null 8.Rb3 null 9.Rb6 null 10.b3 null 11.Ba3 null 12.Be7 null 13.Bh4 null 14.Ng5 null 15.e4 null 16.Ke2 null 17.Kd3 null 18.Kc4 null 19.Kb5 null 20.Ka6 null 21.Ka7 null 22.Ba6
``````

Other ideas :

1.b4 2.b5 3.b6 4.b7 5.b8=B 6.Be5 7.Beb2 8.c3 9.Qa4 10.Qa6 11.a4 12.a5 13.Ra4 14.Rh4 15.Rh5 16.h4 17.Rh3 18.Rf3 19.g3 20.Bh3 21.Bf5 22.Bc2 23.d3 24.Kd2 25.Ke3 26.Kd4 27.Kc5 28.Kb6 29.Ka7 (C+)

1.b4 2.b5 3.b6 4.b7 5.b8=B 6.Be5 7.Beb2 8.c3 9.Qa4 10.Qa7 11.a4 12.a5 13.Ra4 14.Rg4 15.Rg5 16.g4 17.Bg2 18.Bb7 19.Sf3 20.O-O 21.Kg2 22.Kg3 23.Kf4 24.Ke5 25.Kd6 26.Kc7 27.Kb8 (C+)

1.f4 2.f5 3.f6 4.f7 5.f8=B 6.Bc5 7.Bf2 8.e3 9.Ke2 10.Kd3 11.Kc4 12.Kb5 13.Ka6 14.Bb5 15.Se2 16.Rf1 17.Bg1 18.Rf4 19.Ra4 20.b4 21.Bb2 22.Bf6 23.Sbc3 24.Rb1 25.Rb3 26.Qb1 27.Sc1 (C+)

1.c4 2.c5 3.c6 4.c7 5.c8=B 6.Bf5 7.Bc2 8.d3 9.Kd2 10.Ke3 11.Kf4 12.Kg5 13.Kh6 14.Bg5 15.Sd2 16.Rc1 17.Bb1 18.Rc4 19.Rh4 20.g4 21.Bg2 22.Bc6 23.Sgf3 24.Rg1 25.Rg3 26.Qg1 27.Sf1 (C+)

1.f4 2.f5 3.f6 4.f7 5.f8=B 6.Bc5 7.Bf2 8.e3 9.Bd3 10.Se2 11.Rf1 12.Bg1 13.Rf4 14.Rb4 15.c4 16.Qa4 17.Qa7 18.a4 19.Ra3 20.Rab3 21.Sa3 22.Bb1 23.d3 24.Kd2 25.Kc3 26.Kd4 (C+)

1.a4 2.a5 3.a6 4.a7 5.a8=B 6.Bf3 7.e4 8.Se2 9.Sec3 10.Sa4 11.c3 12.Qb3 13.Qb8 14.b4 15.b5 16.b6 17.Bb5 18.O-O 19.Re1 20.Re3 21.Bfe2 22.Rh3 23.Rh4 24.h3 25.Kh2= (C+)

1.h4 2.h5 3.h6 4.h7 5.h8=B 6.Bc3 7.d4 8.Bf4 9.e3 10.Ke2 11.Kf3 12.Kg4 13.Kh5 14.Qg4 15.Be2 16.Bf3 17.Se2 18.Rd1 19.Be1 20.Sd2 21.Rac1= (C+)

1.h4 2.h5 3.h6 4.h7 5.h8=B 6.Bc3 7.d4 8.Sd2 9.Sdf3 10.Sh4 11.f3 12.Kf2 13.Kg3 14.Kg4 15.Kh5 16.g4 17.Bh3 18.Qf1 19.Be1 20.c3= (C+)

1.h4 2.h5 3.h6 4.h7 5.h8=B 6.Bc3 7.Bb4 8.c3 9.Qa4 10.Qa8 11.a4 12.a5 13.a6 14.Ra5 15.Rah5 16.R5h2 17.Sh3 18.Rg1 19.Rhh1= (C+)

1.h4 2.h5 3.Rh4 4.Ra4 5.b4 6.Bb2 7.Be5 8.Bh2 9.g3 10.Bh3 11.Kf1 12.Kg2 13.Kf3 14.Ke4 15.Nf3 (simply 15.Kd5 16.Kc6 17.Kb7 18.Ka8 is also 18 moves) 16.Qh1 17.Bg1 18.Qh2

1.a4 2.a5 3.Ra4 4.Rg4 5.g4 6.Bg2 7.Bd5 8.Ba2 9.b3 10.Ba3 11.Bf8 12.Na3 13.Qa1 14.Kd1 15.Kc1 16.Kb2 17.Qc1 18.Bb1 19.Ka2

1.a4 2.a5 3.Ra4 4.Rg4 5.f4 6.Kf2 7.Kg3 8.Kh4 9.Kh5 10.h4 11.Rh3 12.Rd3 13.g3 14.Bg2 15.Ba8 16.Nf3 17.Qh1 18.Ne1 19.Qb7 and maybe 20.Ng2

• Your 30 is C+ by Jacobi: wismuth.com/jacobi/latest/solver.html I used this code: EnglishN forsyth 8/8/8/8/8/8/PPPPPPPP/RNBQKBNR stipulation ser-a=>b30.0 forsyth K7/1B6/5B2/8/6PQ/1PN2N2/1RPPPP1P/1B3R2 Oct 29, 2022 at 17:41
• Btw, you can change Jacobi output to the regular "N" underneath "Output language:", next to the pause/resume. Nov 5, 2022 at 10:24
• "EnglishN" is a command to recognize "N" a knight instead of nightrider, so we don't have to edit the FEN every single time. Unless specified, Jacobi only accepts "S" as knight, hence the existence of the command. Nov 6, 2022 at 16:33

Here is an attempt of 8 moves:

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. h4 null 2. h5 null 3. h6 null 4. h7 null 5. h8=N null 6. Nf7 null 7. Nd6 null 8. Nb5
``````
• 6.Ng6 7.Rh8 8.Ra8 9.Nf8 is a funny way to make two pieces interact. Nov 4, 2022 at 9:24

I can manage 10 moves.

``````[FEN "8/8/8/8/8/8/PPPPPPPP/RNBQKBNR w - - 0 1"]

1. Nf3 null 2. Nd4 null 3. f3 null 4. Kf2 null 5. Ke3 null 6. Ke4 null 7. Kd5 null 8. Kc6 null 9. Kb7 null 10. Ka8
``````

Note that the only way for the knight to reach d4 in two moves is if it makes both its moves before the pawn moves, and hence before the king moves. Once the knight is on d4, there is only one route for the king to reach a8 in seven moves.