Letter #11 -  2009

Sub:    Something of interest
Date:   3/02/2009 7:02:27 PM EDT
From:  Sole891
To:      service@chess-poster.com

Hello,

I found the following information on a web blog which I believe is very informative and interesting. Hope you guys like it and put it on your nice site.

Thank you,
S. T. USA

Dear viewer,

Thank you for this article that we have found very good and we believe our Chess viewers will enjoy it:

By Adam Revan24

“Here is how I found what I believe to be the largest Chess game possible. Remember the 50th move rule, which states that every 50 moves, a Pawn move or a capture must be made. This ensures that there is a finite number of possible moves. We will assume that black or white can move on the 50th move to make things simple.

Four of black's Pawns will capture four white pieces (not white Pawns), and four of white's Pawns will capture four black pieces. This enables 16 Pawns to move 6 spaces each, and 16*6=96. How many pieces are left to be captured?: 32 pieces -8 captured pieces=24. Actually, 22 pieces will be captured because the two Kings can't be captured. BUT, when the two Kings are left, they will move 50 additional moves until the game is a draw. So that is like "capturing" a King. 24 pieces -1 King = 23 pieces.

Multiply 50 by the sum of 96 and 23, because 50 moves ensue before a capture or Pawn move, and you get 119*50 which equals 5950. This is close to the number 5949, which one website (chess-poster.com) has posted. This is not correct because we must now calculate how many times the captures / Pawn moves SWITCH from black to white, and subtract that number from 5950.

Here's how: at first, 2 black Pawns capture 2 white Knights. Now, black can move 4 pieces (2 Knights, a Rook, and a Bishop for example) onto squares where white Pawns can capture them. In the meantime, white can move his Rooks back and forth while black moves his Knights around or develops his pieces through the openings that the black Pawns created.

This proves that both sides can move around while waiting for the 50th move. When white captures the black pieces, he moves on the 49th move, so we subtract 1 from 5950 to get 5949. After white captures 4 black pieces, the white Pawns can not all promote because two black Pawns still need to capture white's pieces.

So, we need to make another switch. 49 moves after white's Pawn moved, black must make a Pawn capture to get all of his Pawns ready to promote. 5949-1=5948. With black moving on every 50th move, he can promote all of his Pawns. He can't capture all of white's Pawns and pieces because white still has to promote all of his Pawns. So white must move; we need another switch. 5948-1=5947.

Now, with white making a capture/Pawn move every 50 moves, he can now capture all of black's pieces except the black King. Note: white can position his Knights (Pawns can promote into Knights) in order to shield the white Rooks, Bishops, and Queen(s) from checkmating the black King while he is alone. We need one more switch; the black King must now capture all of the white pieces! 5947-1=5946.

After there are two Kings on the board, they move 50 more times until the game is a draw. As you can see, most of the time, there are 50 move intervals between Pawn moves/captures, whether they were made by white or black. There are only four 49 move intervals between Pawn moves/captures, as I just showed, which is why I subtracted 4 from 5950. I simulated part of this game to explain below (only around 20 moves, not 5000!).

Please comment if you disagree or have an alternate solution that gives more moves. I would like to know why someone calculated 5949 moves. That is only 3 apart from what I calculated, so I'm sure our solutions are similar. Note that this may not be the best solution; of all the solutions I could think of, this was the largest number of moves.”

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