# What is the longest possible sequence of double checks?

It is a known record for most number of mutual checks in a row. This made me wonder what the most number of possible double checks in a row is. Only one side can deliver a double check of course.

I have four catergories that I have come up with. Promoted pieces allowed and not allowed. That means that the position can’t start out with promtoed piece’s, but it is allowed once the position starts. The first move/double check is permitted to be a promotion, however.

For each of these are two catergories-forced and unforced. Unforced is where the checked player willing moves into the next square where the double check will occur. Forced is where they have no other options.

Rules:

1. If checkmate occurs, the mating move only counts if it was a double check.

2. Threefold repetition and the 50 move apply, i.e a position can only come two times. The sequence automatically ends upon the third repitition of a position. (I would do it on the last move as it would stil contribe to the count, even if it ends the game.)

3. No infinite loops allowed, even they are possible.

4. The position must be legally reachable and contain only legap move.

5. If a game is forced, and it beats the record for unforced, it is allowed to contend for both titles.

I’ll give you my reasearch on what I could find. The question here is this: Can you find more?

No Promoted Pieces, Unforced-6 Double Checks

``````[FEN "4K3/8/8/3p4/k1p1N3/1p4N1/P5BB/RRQ5 w - - 0 1"]

1. axb3+ Kb5 2. bxc4+ Kc6 3. cxd5+ Kxd5 4. Nc3+ Kd6 5. Nf5+ Kc5 6. Na4#
``````

No Promoted Pieces, Forced-5 Double Checks

``````[FEN "kb1r4/P1p5/1P2P3/6NB/7B/8/8/RRQ4K w - - 0 1"]

1. axb8=Q+ Kxb8 2. bxc7+ Kc8 3. cxd8=Q+ Kxd8 4. Nf7+ Ke8 5. Nd6+ Kf8 *
``````

Promoted Pieces, Unforced-9 Double Checks

``````[FEN "K5b1/5p2/4p3/3pR3/k1p1N1N1/1pQ5/P1B5/RR1R1RRR w - - 0 1"]

1. axb3+ Kb5 2. bxc4+ Kc6 3. cxd5+ Kd7 4. dxe6+ Ke8 5. exf7+ Kf8 6. fxg8=Q+ Kxg8 7. Nh6+ Kh7 8. Nf6+ Kh8 9. Nf7# *
``````

Promoted Pieces, Forced-8 Double Checks

``````[FEN "K4Bb1/5p2/4p3/3p4/k1p3N1/1pR5/P1B5/RQ1RRRRR w - - 0 1"]

1. axb3+ Kb5 2. bxc4+ Kc6 3. cxd5+ Kd7 4. dxe6+ Ke8 5. exf7+ Kxf8 6. fxg8=Q+ Kxg8 7. Nh6+ Kh8 8. Nf7#
``````

This is now outdated. but I’m keeping it here for asthetic purposes. It’s a beautiful, intricate, and well oiled-machine!

``````[FEN "3B1Q2/2N2N1R/3N1B2/N3N1B1/5N1B/3B2N1/2K2k2/R7 w - - 0 1"]

1. Nh1+ Ke3 2. Ng2+ Kd4 3. Nf3+ Kc5 4. Ne4+ Kb6 5. Nd5+ Ka7 6. Nc6+ Kb7 7. Nfd6+
``````

Good luck finding more!

Side Note:

As Hauke Reddmann noted in a comment, Ba1 Bb1 Rb2-Kc3 is a well-known mechanism. However, he does not state where he knows it from. I found a problem that uses it where the mainline has 13 double checks in a row in the mainline. I found in in the YACPBD chess problem database.

``````[Title "Стојнић, Драган Бабић, Миломир, The Problemist 2004-05, #13"]
[FEN "3q1nKB/R1P1kPRB/N3p3/1p1n2p1/2r2p2/1p2b3/P2pb2N/3r4 w - - 0 1"]

1. c8=N+ Kf6 2. Rg6+ Kf5 3. Rf6+ Ke5 4. Rf5+ Ke45. Re5+ Kd4 6. Re4+ Kd3 7. Rd4+ Kc3 8. Rd3+ Kc2 9. Rc3+ Kb2 10. Rc2+ Kb1 11. Rb2+ Ka1 12. Rb1+ Kxa2 13. Nb4#
``````

However it is not entirely forced because of the possibility of 10... Ka3 by black. I see no way to cover that sqaure without interferring with the sequence, at least so far. Otherwise we could have 13-more than Evargalo's sweet 12.

But the mechanism was actually first shown a century ago as @Evargalo suggested in a comment. Indeed it is from a a century ago-quite literally-from what I found here here.

``````[Title "Alain Campbell White, Pittsburgh Gazette Times 4/1916 #12"]
[FEN "2q5/2pp4/3pr3/4pb2/K1p2pn1/2bn1kp1/3pr1R1/6BB w - - 0 1"]

1. Rf2+ Ke3 2. Rf3+ Ke4 3. Re3+ Kd4 4. Re4+ Kd55. Rd4+ Kc5 6. Rd5+ Kc6 7. Rc5+ Kb6 8. Rc6+ Kb7 9. Rb6+ Ka7 10. Rb7+ Ka8 11. Ra7+ Kb8 12. Ra8#
``````
• It's possible there's a "downvote campaign" against you because all of your questions recently have very little to do with actual chess. Your questions instead focus on esoteric parts of the game; the answers to these questions don't actual help anyone in any way besides being passably interesting. I don't mean to be harsh, but why do you even care about any of these questions? – NoseKnowsAll Apr 8 '19 at 4:54
• That being said, I personally upvoted your question because it's technically relevant to chess, and it's a well-formulated question. – NoseKnowsAll Apr 8 '19 at 4:55
• Consder it a hobby. – Rewan Demontay Apr 8 '19 at 4:55
• @NoseKnowsAll I disagree -- chess problems and chess construction tasks are very much part of actual chess. This question is on topic. – Rosie F Apr 8 '19 at 7:54
• Ba1 Bb1 Rb2 - Kc3 is a well known mechanism. 11 double checks. Also, the downvoters may have a point insofar as this SE is more dedicated to OTB than problem chess (still, I earned tons of undeserved upvotes by just quoting a position I happened to know from another forum, answering a problem chess question :-). That said, why don't you carry your question to the MatPlus forum, where the problem chess enthusiasts sit? They will be most interested (and also beat your records in no time :-) – Hauke Reddmann Apr 8 '19 at 7:54

I am pretty sure I could make this last longer, but here is already a sequence with 26 unforced consecutive double-checks without promoted pieces.

``````[FEN "8/8/8/Rp2p3/3Pk1N1/6pB/1Q2N2B/K3R3 w - - 0 1"]

1. Nc3+ Kxd4 2. Ne2+ Ke4 3. Nc3+ Kd4 4. Ne2+ Ke4 5. Nc3+ Kd4 6. Nxb5+ Kd5 7. Nc3+ Kd4 8. Nb5+ Kd5 9. Nc3+ Kd4 10. Ne2+ Ke4 11. Nxg3+ Kf4 12. Ne2+ Ke4 13. Nc3+ Kd4 14. Nb5+ Kd5 15. Nc3+ Kd4 16. Ne2+ Ke4 17. Ng3+ Kf4 18. Ne2+ Kf5 19. Nh6+ Ke4 20. Ng3+ Kf4 21. Ne2+ Ke4 22. Nc3+ Kd4 23. Nb5+ Kd5 24. Nc3+ Kd4 25. Nb5+ Kd5 26.Nc7+
``````

12 forced double-checks, based on the scheme given by Hauke Reddmann in a comment:

``````[FEN "1RN5/5p2/7p/3P3p/2P3p1/QPk4N/1R1p1K2/BB6 w - - 0 1"]

1. Rc2 Kd3 2. Rc3 Kd4 3. Rd3 Ke4 4. Rd4 Ke5 5. Re4 Kf5 6. Re5 Kf6 7. Rf5 Kg6 8. Rf6 Kg7 9. Rg6 Kh7 10. Rg7 Kh8 11. Rh7 {11. Rg8} Kg8 12.Ne7
``````
• I am afraid afraid your clarification isn't very clear to me. If you allow a position to occur three times rather than two (but why would you?), the same example can offer circa 35 consecutive double-checks. – Evargalo Apr 8 '19 at 13:52