# The longest possible chess game

.

The trick is, while black is moving first, he can do more than move pawns, he can capture both of white's knights.

So then you have to ask, but if you're only opening 2 files instead of 4, does that actually make a difference?

The answer is yes. Instead of each side opening 4 files, you can have black open 2, and then have white make the other 6 pawn captures.

First phase black sets up this pawn structure

Now the turns switch and it's white to make captures and pawn moves. During this phase he promotes all his pawns and capture all of black's pieces.

Now it's black's turn to make pawn moves and captures again. He promotes all his pawns and captures all of white's pieces.

And finally the last phase. White captures all of black's remaining pieces.

And that's how you can do it with only 3 switches, and so the longest game with 50 move rule is

(118 x 100) - 3 = 11797 ply or 5898.5 moves (the game ends on white's 5899th move)

WolfKid18 wrote:

too bad the analysis board doesn't understand repetition or 50-move rule, i could experiment with it forever

Playing with a real board was a useful way for me to wrap my head around this problem and solution. You just tell yourself that each pawn move and capture represents the 49.5 moves that came behind it.

Any move that isn't a capture or pawn move you can ignore.

When you do that, here's a representation of what the longest game looks like:

(Hard to notice, but moves 29, 109, and 171 marked with "switch")

Just 183 moves??

llama wrote:

The trick is, while black is moving first, he can do more than move pawns, he can capture both of white's knights.

So then you have to ask, but if you're only opening 2 files instead of 4, does that actually make a difference?

The answer is yes. Instead of each side opening 4 files, you can have black open 2, and then have white make the other 6 pawn captures.

First phase black sets up this pawn structure

Now the turns switch and it's white to make captures and pawn moves. During this phase he promotes all his pawns and capture all of black's pieces.

Now it's black's turn to make pawn moves and captures again. He promotes all his pawns and captures all of white's pieces.

And finally the last phase. White captures all of black's remaining pieces.

And that's how you can do it with only 3 switches, and so the longest game with 50 move rule is

(118 x 100) - 3 = 11797 ply or 5898.5 moves (the game ends on white's 5899th move)

I expected more

Pawned064 wrote:

Just 183 moves??

No.

llama wrote:
Pawned064 wrote:

Just 183 moves??

No.

What was that game for?

llama wrote:
WolfKid18 wrote:

too bad the analysis board doesn't understand repetition or 50-move rule, i could experiment with it forever

Playing with a real board was a useful way for me to wrap my head around this problem and solution. You just tell yourself that each pawn move and capture represents the 49.5 moves that came behind it.

Any move that isn't a capture or pawn move you can ignore.

When you do that, here's a representation of what the longest game looks like:

(Hard to notice, but moves 29, 109, and 171 marked with "switch")

I mean, do you even read?

Tell me, what's the point of me trying to have a conversation with someone who doesn't understand English?

llama wrote:

*blahblahblah*

OK.

llama wrote:

I mean, do you even read?

Tell me, what's the point of me trying to have a conversation with someone who doesn't understand English?

-_-

Pawned064 wrote:
llama wrote:

I mean, do you even read?

Tell me, what's the point of me trying to have a conversation with someone who doesn't understand English?

-_-

Can't believe a llama just did that.

Oh, you must not have known me very long. Sometimes I'm not very nice.

I have no idea. How many moves are possible? GM Yasser Seirawan gives the number of possible moves in a chess game at time 26:26 in this video - 10 to the 56th power!! (By the way, a very funny video as he talks about how poorly he played some of his earliest games, including a checkmate on him that wasn't, that he agreed with!)

Pawned064 wrote:

...  and so the longest game with 50 move rule is

(118 x 100) - 3 = 11797 ply or 5898.5 moves (the game ends on white's 5899th move)

I expected more

Claims under the 50 move rule are optional (and no longer included in the FIDE basic chess rules).  The 75 move rule included in the competition rules is mandatory, so in either case your expectation is correct.

Under basic rules infinite games are allowed (but none of these have finished yet). This was also true under previous basic rules because claims under the triple repetition rule included in those were also optional.

MARattigan wrote:
Pawned064 wrote:

...  and so the longest game with 50 move rule is

(118 x 100) - 3 = 11797 ply or 5898.5 moves (the game ends on white's 5899th move)

I expected more

Claims under the 50 move rule are optional (and no longer included in the FIDE basic chess rules).  The 75 move rule included in the competition rules is mandatory, so in either case your expectation is correct.

Under basic rules infinite games are allowed (but none of these have finished yet).

For chess.com it's 5898.5 moves because (unlike before) they auto claim it on move 50.

For the 75 move rule it's 8848.5 moves

llama wrote:

...

For chess.com it's 5898.5 moves because (unlike before) they auto claim it on move 50.

But that means that the games on chess.com are strictly speaking not chess games since they don't follow the laws of chess.

Legalistic ideologies are intrinsically dumb.