# [Retros] The Longest Chess Game

peufe at tin.it peufe at tin.it
Thu Jun 14 11:02:56 EDT 2007

from :
Franco Fedeli
Italy

Hi friends,
I asked myself: " How much long could be a chess game
before one of the players has the right to claim a draw first time?"
(Articles 9.2 and 9.3 FIDE Laws of Chess)
It is easy to see that the longest chess game is one among that
with the slowest possible pawn moves and pieces captures, and with
all pawns promoted.
So it is like that:
Moves :
1 to 49 : Knight moves ( avoiding to repeat the same position the third
time)

50 : white moves a pawn one step

...50 - 99 Officers Moves

100 : White one step pawn move
and so on till all white pawns are on the fifth rank :
8*3*50= 1200

1200 : the last white pawn goes on the fifth rank

1249 : Black sacrifices a Knight on h6

1250 : hxNh6
and so on......

Summary :
Every pawn moves 6 times.
W pawns moves after 50 moves.
B pawns moves after 49 moves ( in order the Black doesn't have the right to
claim the draw)
W sacrifices 4 pieces to allow all black pawns promotions
B sacrifices 4 pieces to allow all white pawns promotions

White pawns moves : 8*6=48
Black pawns moves : 8*6=48

Total moves till all pawns are promoted:
48*50+48*49= 4752

After pawns promotions each colour has 11 pieces and king.
Game goes on taking a Black piece every 50 moves and a White piece every 49
moves.
White captures all 11 Black pieces after 11*50 = 550 moves.
Black captures 10 white pieces ( except Q or R in order to avoid draw
because
" dead position" Art. 5.2) after 10*49= 490 moves.
Then other 50 moves till Black acquires the right to claim for a draw.

So: 4752+550+490+50 = 5842

The longest game is 5842 moves long.
It ends with a draw ( if Black claims).
Another quite impossible question is:
"How many different longest chess games are there?"

Bye,

Franco Fedeli