Answers.Body: <p>After going through a <a href="https://www.chessgames.com/perl/chesscollection?cid=1006143" rel="noreferrer">list</a> of games with king hunts, I found <a href="https://www.chessgames.com/perl/chessgame?gid=1013231" rel="noreferrer">game</a> at last in which 6 pieces are involved in the mate!</p>
  
  <pre><code>[Title "Alexander Alekhine-NN, Simul 34b, Moedling Austria, 3/24/1936"]
  [FEN ""]
  [startply "33"]
  
  1. e4 e5 2. d4 f6 3. dxe5 fxe5 4. Qh5+ Ke7 5. Qxe5+ Kf7 6. Bc4+ d5 7. Bxd5+ Kg6 8. Qg3+ Kh5 9. Bf7+ g6 10. h3 Qf6 11. Nf3 Be7 12. Qg4+ Bxg4 13. hxg4+ Kxg4 14. Nh2+ Kh4 15. Nf1+ Kg4 16. Be6+ Qxe6 17. f3#
  </code></pre>
  
  <p>The Bc1 prevents the Black king from moving to f4 and g5, the e4 pawn covers f5, the f3 pawn is giving mate, the Nf1 covers g3, the g2 pawn protects the mating piece and covers h3, and the Rh1 covers the h3, h4, and h5 squares.</p>
  
  <hr>
  
  <p>Upon seeing this question, I remembered entry #355 of <a href="https://timkr.home.xs4all.nl/chess2/diary_18.htm" rel="noreferrer">Tim Krabbe’s Chess Diary</a>, which gives some examples of checkmates involving all four minor pieces. The best and simplest example is <a href="https://www.chessgames.com/perl/chessgame?gid=1358125&amp;kpage=1#kibitzing" rel="noreferrer">this</a> game. </p>
  
  <pre><code>[Title "Vasily Borisovich Malinin-Viktor Savinov, Leningrad Russia, 1988"]
  [FEN ""]
  [startply "71"]
  
  1. d4 Nf6 2. c4 c5 3. d5 b5 4. cxb5 a6 5. bxa6 Bxa6 6. Nc3 d6 7. Nf3 g6 8. g3 Bg7 9. h4 O-O 10. h5 Nbd7 11. hxg6 hxg6 12. Bh3 Re8 13.  Qc2 Rb8 14. Be3 Nxd5 15. Qxg6 fxg6 16. Be6+ Kf8 17. Nxd5 Rxb2 18. Ng5 Nf6 19. Nf4 Qa5+ 20. Kf1 Bxe2+ 21. Kg1 Reb8 22. Bf7 Rb1+ 23. Kh2 Ng4+ 24. Kh3 Rxh1+ 25. Rxh1 Nxf2+ 26. Bxf2 Bg4+ 27. Kxg4 Rb4 28. Kf3 Qa3+ 29. Be3 Qa8+ 30. Bd5 Qa5 31. Nfe6+ Kg8 32. Nc7+ e6 33. Bxe6+ Kf8 34. Nh7+ Ke7 35. Bg5+ Bf6 36. Bxf6#
  </code></pre>
  
  <p>This is easily deduced to be a <a href="https://en.m.wikipedia.org/wiki/Pure_mate" rel="noreferrer">pure mate</a>, thus raising the known record to four pieces.</p>
  
  <p>Also, to user @John Coleman from the comments, here’s a <a href="https://www.chessgames.com/perl/chessgame?gid=1553589" rel="noreferrer">king hunt</a>, with four pieces, for you. :-)</p>
  
  <pre><code>[Title "Roland Schmaltz-Ronen Har-Zvi, Internet Chess Club, 3/7/2001"]
  [FEN ""]
  [startply "48"]
  
  1. e4 Nc6 2. Nc3 e5 3. g3 Bc5 4. Bg2 Nf6 5. Nge2 d6 6. h3 Bb6 7. O-O O-O 8. Kh2 Re8 9. f4 exf4 10. gxf4 Ng4+ 11. Kg3 Nf2 12. Rxf2 Qh4+ 13. Kxh4 Bxf2+ 14. Ng3 Re6 15. Kg4 Nd4 16. f5 Rg6+ 17. Kf4 Rxg3 18. Qf1 g5+ 19. fxg6 Ne6+ 20. Kf5 Ng7+ 21. Kf6 Rxg6+ 22. Ke7 Re6+ 23. Kd8 Bb6 24. Nd5 Re8#
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T14:31:58.013Z
Answers.Text: Nice find! Thanks! =)
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T15:18:40.967Z
Answers.Text: Hey I managed to find a historical game with also 4 involved pieces, but of all different types! =)
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T17:43:13.773Z
Answers.Text: Nice 6-piece mate! Though it's arguably not a competitive game because most simul games are with complete amateurs haha. =)
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T14:23:27.237Z
Answers.LastActivityDate: 2020-05-16T17:21:20.220Z
Answers.LastEditDate: 2020-05-16T17:21:20.220Z
Answers.UserDisplayName: Rewan Demontay
Answers.Body: <p>It took a while, but I found via youtube <a href="https://www.youtube.com/watch?v=SFeCTEFJoeg" rel="nofollow noreferrer">an old well-known game with a king hunt ending in checkmate with 5 involved pieces</a>!</p>
  
  <pre><code>[Title "Josef Matschego − Ernst Falkbeer , Vienna (1853)"]
  [FEN ""]
  [startply "50"]
  
  1. e4 e5 2. f4 exf4 3. Nf3 g5 4. h4 g4 5. Ne5 Nf6 6. Nc3 d6 7. Nc4 Be7 
  8. d4 Nh5 9. Be2 Bh4 10. Kd2 Qg5 11. Kd3 Nc6 12. a3 Bf2 13. Nd5 Bd4 
  14. Nc7 Kd8 15. Nd5 f5 16. Nd6 fxe4 17. Kc4 Qd5 18. Kd5 Nf6 19. Kc4 Be6 
  20. Kb5 a6 21. Ka4 b5 22. Nb5 axb5 23. Kb5 Ra5 24. Kc6 Bd5 25. Kd6 Ne8#
  </code></pre>
  
  <p>Interestingly, from move 17 onwards it is a mate in 9, and the only way to achieve that is via sacrificing the queen first!</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T22:42:56.750Z
Answers.Text: It is even five involved pieces, I believe, or am I double counting?
Answers.UserDisplayName: Vincent
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-17T03:23:52.430Z
Answers.Text: @Vincent: Lol! I don't know how I miscounted that!
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-17T09:56:13.767Z
Answers.Text: Shocked to see Mr Falkbeer playing 2 ...exf4 !
Answers.UserDisplayName: James Martin
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-18T04:22:35.303Z
Answers.Text: @JamesMartin: Can you elaborate on why it is shocking to you? Stockfish 10+ on Lichess at depth 40 thinks it is in fact the best move.
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-18T07:46:17.990Z
Answers.Text: @user21820 Ah, I wasn't being too serious, but Falkbeer has a defence to the King's Gambit named after him, the "Falkbeer Counter Gambit", which is 2 ...d5.
Answers.UserDisplayName: James Martin
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-18T08:30:06.883Z
Answers.Text: @JamesMartin: Ahh I see! So [Wikipedia](https://en.wikipedia.org/wiki/King's_Gambit,_Falkbeer_Countergambit) says that Falkbeer "played it in an 1851 game against Adolf Anderssen", so I guess 2 years later he figured out the 'right' move? =P
Answers.UserDisplayName: user21820
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-05-16T15:17:20.753Z
Answers.LastActivityDate: 2020-05-17T03:24:11.933Z
Answers.LastEditDate: 2020-05-17T03:24:11.933Z
Answers.UserDisplayName: user21820
Body: <p>I recall seeing a number of chess games where a lot of pieces are involved in the final checkmate, and was curious to know what is the maximum number of pieces of one player A that have been involved in a checkmate of the other player B, where a piece is said to be involved if and only if removing it either causes B's king to be no longer in check or causes one of the squares around B's king to be no longer attacked by A's pieces. It is easy to construct a reachable position where 9 pieces are involved, and to prove that no more than 9 pieces are involved. It is also possible for all 6 types of pieces to be involved. For example:</p>
  
  <pre><code>[White "Checkmate"]
  [Black "9 pieces involved"]
  [FEN "6B1/7K/2N5/5kP1/2R1P2P/8/6N1/3Q4 w - - 0 1"]
  </code></pre>
  
  <p>But are there any actual competitive games that ended with such a checkmate (i.e. using 9 pieces)? If not, what is the maximum number ever used in a competitive game? Among these games, what is the maximum number of types of pieces used? I exclude non-competitive games merely to avoid contrived games.</p>
  
  <p>Note: As John Coleman pointed out in the comments, this notion of "involved" is more like "critically involved" because it is possible that a checking piece is covering another piece that would also provide check if the first was removed, or that a piece next to the checkmated king is protected by more than one piece. One could consider a variant notion of "loosely involved" defined as follows: A piece X of A is loosely involved in a checkmate of B if and only if we can remove some pieces of A that attack B's king or a square next to B's king such that it is still a checkmate and X is (critically) involved. I think this should cover such cases, so I am fine with including examples that use this looser definition of "involved".</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T12:05:19.330Z
Comments.Text: Looking at the position that you give, a good bet is that the answer will be the end-position of a successful king hunt.
Comments.UserDisplayName: John Coleman
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T13:41:32.833Z
Comments.Text: @JohnColeman: Yup! Though I kind of suspect the maximum that comes up in an actual competitive game would be merely 5 or 6. It may be worth noting that [well-known examples of pure mate](https://en.m.wikipedia.org/wiki/Pure_mate) only reach 3 involved pieces, but since my criterion allows non-pure mates, there may be other well-known checkmates involving more pieces.
Comments.UserDisplayName: user21820
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T14:05:28.257Z
Comments.Text: That is a rather odd definition of "involved". Surely a piece belonging to A is involved if removing it would stop B being in checkmate? With this definition it is possible for more than 9 pieces to be involved, if some of them prevent B from interposing another piece. (I think the fact that it is possible to interpose means there will be at most 7 pieces controlling the squares around the king, so you would need at least 3 pieces involved in this way to beat 9, but that is certainly possible.)
Comments.UserDisplayName: Especially Lime
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T14:05:31.210Z
Comments.Text: My guess is a maybe king-hunt that terminates on the 4th rank where a solid wall of 3 pawns on the 2nd rank prevent advance, something like a rook is delivering mate on the 4th rank, and 2 or 3 pieces prevent retreat to the 5th. You will, however need to clarify the exact definition of "involved".
Comments.UserDisplayName: John Coleman
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T14:38:32.397Z
Comments.Text: @EspeciallyLime: The reason for my definition was to limit the 'involvement' scope. In your kind of example, it could be that B has many pieces that can be used to block the check if some piece of A is removed. In another kind of example, some pieces of A are blocking B's pieces from attacking A's king. Are those to be counted as well? It is aesthetically pleasing (to me) to count only the pieces that are directly involving in attacking the checkmated king. =)
Comments.UserDisplayName: user21820
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T14:45:40.690Z
Comments.Text: @JohnColeman: I thought that the definition of "involved" in my question was sufficiently precise. But if you want a mathematically precise version: Given a chess position, we say that a piece X attacks a square Y iff ( X can move to Y if every piece at Y is removed ), and we say that a piece X of A is involved in a checkmate iff ( removing X causes one of the 9 squares under or next to B's king to be not attacked by any piece of A ). Is it clear now?
Comments.UserDisplayName: user21820
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T15:26:29.690Z
Comments.Text: The problem with your definition is that if two pieces are blocking off the same retreat square in such a way that it stays covered if only one of those pieces is removed then under your definition neither of those pieces are involved. To me it seems more natural to say that both are involved. I wasn't sure if that was your actual intention. I see now that it is, but if so, I don't think that it is a very good definition. For one thing, you can set up a position where mate is delivered by double check in such a way that under your definition, no pieces are involved in the checkmate.
Comments.UserDisplayName: John Coleman
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T15:28:48.617Z
Comments.Text: @JohnColeman: Thanks for finding that edge case. Unfortunately, as you saw, my precise definition had exactly that issue. Should I modify the definition to fix it (counting the primary attacker but not the covered one), since it doesn't invalidate any of the existing answers?
Comments.UserDisplayName: user21820
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T15:28:56.923Z
Comments.Text: Perhaps "essentially involved" might be a term for the concept that you are defining. Whatever you call it, it is clearly an interesting notion. It seems straightforward to say that pieces can be involved in a checkmate without being essential to the mate.
Comments.UserDisplayName: John Coleman
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-16T22:51:59.740Z
Comments.Text: The rook is not involved in your example. If your queen is on d1, however, then it will be (as the rook will be defending the pawn on e4).
Comments.UserDisplayName: Carl-Fredrik Nyberg Brodda
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-05-17T03:25:27.827Z
Comments.Text: @Carl-FredrikNybergBrodda: Oops I moved the queen and failed to check. Too careless. Will fix now.
Comments.UserDisplayName: user21820
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-08-05T07:51:59.920Z
Comments.Text: @CitrusCornflakes: Obviously, otherwise why would I post this? Please read my questions starting from "If not, what is the maximum number ...?".
Comments.UserDisplayName: user21820
Tags: <checkmate><records>
Title: Most pieces involved in checkmate in actual game?
ThreadText: # Most pieces involved in checkmate in actual game?
  
  (Asked by: username_0 on 2020-05-16)
  
  I recall seeing a number of chess games where a lot of pieces are involved in the final checkmate, and was curious to know what is the maximum number of pieces of one player A that have been involved in a checkmate of the other player B, where a piece is said to be involved if and only if removing it either causes B's king to be no longer in check or causes one of the squares around B's king to be no longer attacked by A's pieces. It is easy to construct a reachable position where 9 pieces are involved, and to prove that no more than 9 pieces are involved. It is also possible for all 6 types of pieces to be involved. For example:
  [White "Checkmate"]
  [Black "9 pieces involved"]
  [FEN "6B1/7K/2N5/5kP1/2R1P2P/8/6N1/3Q4 w - - 0 1"]
  
  But are there any actual competitive games that ended with such a checkmate (i.e. using 9 pieces)? If not, what is the maximum number ever used in a competitive game? Among these games, what is the maximum number of types of pieces used? I exclude non-competitive games merely to avoid contrived games.
  Note: As username_1 pointed out in the comments, this notion of "involved" is more like "critically involved" because it is possible that a checking piece is covering another piece that would also provide check if the first was removed, or that a piece next to the checkmated king is protected by more than one piece. One could consider a variant notion of "loosely involved" defined as follows: A piece X of A is loosely involved in a checkmate of B if and only if we can remove some pieces of A that attack B's king or a square next to B's king such that it is still a checkmate and X is (critically) involved. I think this should cover such cases, so I am fine with including examples that use this looser definition of "involved".
  
  **Tags:** checkmate, records
  
  > **Comments:**
  > **username_1**: Looking at the position that you give, a good bet is that the answer will be the end-position of a successful king hunt.  
  > **username_0**: @JohnColeman: Yup! Though I kind of suspect the maximum that comes up in an actual competitive game would be merely 5 or 6. It may be worth noting that [well-known examples of pure mate](https://en.m.wikipedia.org/wiki/Pure_mate) only reach 3 involved pieces, but since my criterion allows non-pure mates, there may be other well-known checkmates involving more pieces.  
  > **username_2**: That is a rather odd definition of "involved". Surely a piece belonging to A is involved if removing it would stop B being in checkmate? With this definition it is possible for more than 9 pieces to be involved, if some of them prevent B from interposing another piece. (I think the fact that it is possible to interpose means there will be at most 7 pieces controlling the squares around the king, so you would need at least 3 pieces involved in this way to beat 9, but that is certainly possible.)  
  > **username_1**: My guess is a maybe king-hunt that terminates on the 4th rank where a solid wall of 3 pawns on the 2nd rank prevent advance, something like a rook is delivering mate on the 4th rank, and 2 or 3 pieces prevent retreat to the 5th. You will, however need to clarify the exact definition of "involved".  
  > **username_0**: @EspeciallyLime: The reason for my definition was to limit the 'involvement' scope. In your kind of example, it could be that B has many pieces that can be used to block the check if some piece of A is removed. In another kind of example, some pieces of A are blocking B's pieces from attacking A's king. Are those to be counted as well? It is aesthetically pleasing (to me) to count only the pieces that are directly involving in attacking the checkmated king. =)  
  > **username_0**: @JohnColeman: I thought that the definition of "involved" in my question was sufficiently precise. But if you want a mathematically precise version: Given a chess position, we say that a piece X attacks a square Y iff ( X can move to Y if every piece at Y is removed ), and we say that a piece X of A is involved in a checkmate iff ( removing X causes one of the 9 squares under or next to B's king to be not attacked by any piece of A ). Is it clear now?  
  > **username_1**: The problem with your definition is that if two pieces are blocking off the same retreat square in such a way that it stays covered if only one of those pieces is removed then under your definition neither of those pieces are involved. To me it seems more natural to say that both are involved. I wasn't sure if that was your actual intention. I see now that it is, but if so, I don't think that it is a very good definition. For one thing, you can set up a position where mate is delivered by double check in such a way that under your definition, no pieces are involved in the checkmate.  
  > **username_0**: @JohnColeman: Thanks for finding that edge case. Unfortunately, as you saw, my precise definition had exactly that issue. Should I modify the definition to fix it (counting the primary attacker but not the covered one), since it doesn't invalidate any of the existing answers?  
  > **username_1**: Perhaps "essentially involved" might be a term for the concept that you are defining. Whatever you call it, it is clearly an interesting notion. It seems straightforward to say that pieces can be involved in a checkmate without being essential to the mate.  
  > **username_3**: The rook is not involved in your example. If your queen is on d1, however, then it will be (as the rook will be defending the pawn on e4).  
  > **username_0**: @Carl-FredrikNybergBrodda: Oops I moved the queen and failed to check. Too careless. Will fix now.  
  > **username_0**: @CitrusCornflakes: Obviously, otherwise why would I post this? Please read my questions starting from "If not, what is the maximum number ...?".  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_0 on 2020-05-16. Score: 5 | Accepted answer
  
  It took a while, but I found via youtube an old well-known game with a king hunt ending in checkmate with 5 involved pieces!
  [Title "Josef Matschego − Ernst Falkbeer , Vienna (1853)"]
  [FEN ""]
  [startply "50"]
  
  1. e4 e5 2. f4 exf4 3. Nf3 g5 4. h4 g4 5. Ne5 Nf6 6. Nc3 d6 7. Nc4 Be7 
  8. d4 Nh5 9. Be2 Bh4 10. Kd2 Qg5 11. Kd3 Nc6 12. a3 Bf2 13. Nd5 Bd4 
  14. Nc7 Kd8 15. Nd5 f5 16. Nd6 fxe4 17. Kc4 Qd5 18. Kd5 Nf6 19. Kc4 Be6 
  20. Kb5 a6 21. Ka4 b5 22. Nb5 axb5 23. Kb5 Ra5 24. Kc6 Bd5 25. Kd6 Ne8#
  
  Interestingly, from move 17 onwards it is a mate in 9, and the only way to achieve that is via sacrificing the queen first!
  
  > **Comments:**
  > **username_5**: It is even five involved pieces, I believe, or am I double counting?  
  > **username_0**: @username_5: Lol! I don't know how I miscounted that!  
  > **username_6**: Shocked to see Mr Falkbeer playing 2 ...exf4 !  
  > **username_0**: @JamesMartin: Can you elaborate on why it is shocking to you? Stockfish 10+ on Lichess at depth 40 thinks it is in fact the best move.  
  > **username_6**: @username_0 Ah, I wasn't being too serious, but Falkbeer has a defence to the King's Gambit named after him, the "Falkbeer Counter Gambit", which is 2 ...d5.  
  > **username_0**: @JamesMartin: Ahh I see! So [Wikipedia](https://en.wikipedia.org/wiki/King's_Gambit,_Falkbeer_Countergambit) says that Falkbeer "played it in an 1851 game against Adolf Anderssen", so I guess 2 years later he figured out the 'right' move? =P  
  
  ---
  
  ### Answer by username_4 on 2020-05-16. Score: 9
  
  After going through a list of games with king hunts, I found game at last in which 6 pieces are involved in the mate!
  [Title "Alexander Alekhine-NN, Simul 34b, Moedling Austria, 3/24/1936"]
  [FEN ""]
  [startply "33"]
  
  1. e4 e5 2. d4 f6 3. dxe5 fxe5 4. Qh5+ Ke7 5. Qxe5+ Kf7 6. Bc4+ d5 7. Bxd5+ Kg6 8. Qg3+ Kh5 9. Bf7+ g6 10. h3 Qf6 11. Nf3 Be7 12. Qg4+ Bxg4 13. hxg4+ Kxg4 14. Nh2+ Kh4 15. Nf1+ Kg4 16. Be6+ Qxe6 17. f3#
  
  The Bc1 prevents the Black king from moving to f4 and g5, the e4 pawn covers f5, the f3 pawn is giving mate, the Nf1 covers g3, the g2 pawn protects the mating piece and covers h3, and the Rh1 covers the h3, h4, and h5 squares.
  
  Upon seeing this question, I remembered entry #355 of Tim Krabbe’s Chess Diary, which gives some examples of checkmates involving all four minor pieces. The best and simplest example is this game. 
  [Title "Vasily Borisovich Malinin-Viktor Savinov, Leningrad Russia, 1988"]
  [FEN ""]
  [startply "71"]
  
  1. d4 Nf6 2. c4 c5 3. d5 b5 4. cxb5 a6 5. bxa6 Bxa6 6. Nc3 d6 7. Nf3 g6 8. g3 Bg7 9. h4 O-O 10. h5 Nbd7 11. hxg6 hxg6 12. Bh3 Re8 13.  Qc2 Rb8 14. Be3 Nxd5 15. Qxg6 fxg6 16. Be6+ Kf8 17. Nxd5 Rxb2 18. Ng5 Nf6 19. Nf4 Qa5+ 20. Kf1 Bxe2+ 21. Kg1 Reb8 22. Bf7 Rb1+ 23. Kh2 Ng4+ 24. Kh3 Rxh1+ 25. Rxh1 Nxf2+ 26. Bxf2 Bg4+ 27. Kxg4 Rb4 28. Kf3 Qa3+ 29. Be3 Qa8+ 30. Bd5 Qa5 31. Nfe6+ Kg8 32. Nc7+ e6 33. Bxe6+ Kf8 34. Nh7+ Ke7 35. Bg5+ Bf6 36. Bxf6#
  
  This is easily deduced to be a pure mate, thus raising the known record to four pieces.
  Also, to user @username_1 from the comments, here’s a king hunt, with four pieces, for you. :-)
  [Title "Roland Schmaltz-Ronen Har-Zvi, Internet Chess Club, 3/7/2001"]
  [FEN ""]
  [startply "48"]
  
  1. e4 Nc6 2. Nc3 e5 3. g3 Bc5 4. Bg2 Nf6 5. Nge2 d6 6. h3 Bb6 7. O-O O-O 8. Kh2 Re8 9. f4 exf4 10. gxf4 Ng4+ 11. Kg3 Nf2 12. Rxf2 Qh4+ 13. Kxh4 Bxf2+ 14. Ng3 Re6 15. Kg4 Nd4 16. f5 Rg6+ 17. Kf4 Rxg3 18. Qf1 g5+ 19. fxg6 Ne6+ 20. Kf5 Ng7+ 21. Kf6 Rxg6+ 22. Ke7 Re6+ 23. Kd8 Bb6 24. Nd5 Re8#
  
  > **Comments:**
  > **username_0**: Nice find! Thanks! =)  
  > **username_0**: Hey I managed to find a historical game with also 4 involved pieces, but of all different types! =)  
  > **username_0**: Nice 6-piece mate! Though it's arguably not a competitive game because most simul games are with complete amateurs haha. =)  
  
  ---
  
  