# Why does the 75 move rule apply when the game have a forced checkmate?

In this position for example White has a forced checkmate in 549:

``````[FEN "1n1k4/6Q1/5KP1/8/7b/1r6/8/8 w - - 0 1"]
``````

How is it fair to terminate the game before White could ever force the win?

• Note that the 50-move rule would probably be applied first at the request of the defending player Commented Jul 23 at 15:19
• If you can't find a win here in 75 moves, you won't in 549 moves either. Commented Jul 23 at 17:22
• You should have drunk Borjomi before. And not on the 75th move suddenly start "pumping rights". Commented Jul 24 at 20:45
• Look at this pdf. It explains the evolution of 50 move rule and reasons for bringing the 75 move rule. Commented Jul 26 at 18:54

TL;DR because unaided human players over the board are very unlikely to find the most precise lines in such critical positions.

``````[Title "#549"]
[FEN "1n1k4/6Q1/5KP1/8/7b/1r6/8/8 w - - 0 1"]
``````

Firstly, let's review this position.

The counter for the 75 move rule is set to zero by any pawn move or capture. So here, if we give the position to the syzygy engine it tells us that DTZ is 109 single moves.

The syzygy notation is perhaps a bit misleading here. What it means is that (1) there 9 single moves until the pawn move 5.g7 zeroes the count, and (2) beyond the pawn move lies a "cursed win" of unspecified length, i.e. the 50 move rule allows Black to draw. Syzygy does not engage with the 75 move rule directly.

After 5.g7, syzygy shows DTZ as 102 meaning that two single moves later the counter is zeroed again with 6.g8=N+. Now we enter into the endgame proper with DTZ shown as 1030 single moves, which is the lurking cursed win.

This means with best play, White can force a zeroing move within at most 1030 single moves = 515.0 "double" moves, before White can force a capture.

You can see this play out in sysygy.

Musing over long tablebase wins, Time Krabbé famously mused:

Playing over these moves is an eerie experience. They are not human; a grandmaster does not understand them any better than someone who has learned chess yesterday. The knights jump, the kings orbit, the sun goes down, and every move is the truth. It's like being revealed the Meaning of Life, but it's in Estonian.

But we are mere humans. There is no point giving a limit of 515 moves for humans to progress the game. We do not think in the same way, and we are not going to find these mega wins over the board. But equally, the weaker side will not find the optimal defences. The judges want to go home. So it has been deemed that if progress cannot be made in 75 moves, then the game is a draw.

There are simpler positions where 75 moves are also not sufficient. I don't think there is any 5 piece endgame (but please correct me if I am wrong). However here is a position with 6 pieces where White needs 152.0 moves to zero. Even this simpler position is still beyond human capabilities to find over the board.

``````[Title "DTZ 304 Black to move"]
[FEN "r5r1/8/k7/8/8/8/3K4/1Q4N1 w - - 0 1"]
``````

For this rule to actually trigger requires two player both determined to play on. Their mentality is the opposite of the "arranged draw"! Either could claim a draw but they both choose to play on, until the judge cries: "Enough already!". I am interested to know of any FIDE tournaments in which this rule has actually triggered. I suspect it is more of a theoretical safety net.

Note that it does not apply by default to chess problems, where instead an automatic 50 move rule applies, but only to so-called "retro problems". For most long studies with no retro considerations, there is no termination - just play on until draw by repetition (if the game doesn't come to a natural halt by mate, stalemate or dead position).

• "You can see this play out in YouTube.": the link goes to Syzygy. Did you mean to link to a YouTube video, or perhaps to write "Syzygy" instead of "YouTube"? Commented Jul 23 at 11:38
• Additionally, it is likely that any position in which one side could force a win, but would need more than 75 moves between "zeroes" to do so, will have been preceded by a situation where a win could have been forced without needing to waive the 75-move rule, and a draw that occures because of the 75-move rule will be a result of imperfect play by the side that with perfect play could have forced a win. Commented Jul 23 at 17:46
• No! That's exactly why they refused. Because we found positions where we need 100 moves, 125 moves, and so on. Commented Jul 24 at 20:51
• @ЭлсиРинген you are missing my point. I knew w there are longer checkmates but I am explaining why the 50 move & 75 move rules are still thought to be ok Commented Jul 24 at 22:31

I'll explain the scheme to you. Initially, it was just a rule to stop a meaningless game. No one thought that the number of moves was important. They took 50 of the balda. It's fine!

Then it turned out that 50 moves were not enough for some of the positions won, and exceptions were introduced. In the end, they brought them so much that they themselves realized that some kind of bullshit had turned out.

And they made a reasonable decision: "if you don't have time, you're free."

You can-you can't, it doesn't matter anymore. You lost because you didn't meet the limit of moves. Let you prove at least a hundred times that you will win by force.

But you didn't meet the allotted number of moves! Goodbye, loser!

Well, the rules are just like that:

Won in 50.0 moves - well done! Honor and respect! Won in 50.5 moves - you're a loser! Go home.