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1. 24 Jun '13 22:57
Checkmate is impossible?
2. 24 Jun '13 23:05 / 1 edit
Yep, impossible not enough material to mate.

Best a king can do is limit an opposing king to rank. Best a knight can do is attack two squares on a diagonal, which means if the knight can put the king in check, it can always move to a free square.
3.  ChessPraxis
Cowboy From Hell
24 Jun '13 23:08
Only Swiss Gambit can mate with a lone N.
4.  woodypusher
misanthrope
25 Jun '13 04:55
Originally posted by divegeester
Checkmate is impossible?
Checkmate is also impossible to force with K+N+N v K
5.  woodypusher
misanthrope
25 Jun '13 05:01 / 1 edit
Originally posted by ChessPraxis
Only Swiss Gambit can mate with a lone N.
R J can force mate with lone bishop v king...in the opposite-colored corner, through faith.
6. 25 Jun '13 07:35
Originally posted by woodypusher
R J can force mate with lone bishop v king...in the opposite-colored corner, through faith.
Hallelujah!
7.  moonbus
Uber-Nerd
25 Jun '13 09:18 / 2 edits
Originally posted by woodypusher
Checkmate is also impossible to force with K+N+N v K
This was thought to be impossible until a computer program worked it out. It requires more than 30 moves, however, so, according to tournament rules, this would be a draw. I doubt any human could reproduce the moves.

Wiki has a good article on mate with 2 knights: it is possible if the opposing K is poorly placed.

https://en.wikipedia.org/wiki/Two_knights_endgame#CITEREFSeirawan2003
8.  ChessPraxis
Cowboy From Hell
25 Jun '13 11:24
Originally posted by moonbus
This was thought to be impossible until a computer program worked it out. It requires more than 30 moves, however, so, according to tournament rules, this would be a draw. I doubt any human could reproduce the moves.

Wiki has a good article on mate with 2 knights: it is possible if the opposing K is poorly placed.

https://en.wikipedia.org/wiki/Two_knights_endgame#CITEREFSeirawan2003
Forced being the operative word.
9. 25 Jun '13 11:28 / 1 edit
Originally posted by moonbus
This was thought to be impossible until a computer program worked it out. It requires more than 30 moves, however, so, according to tournament rules, this would be a draw. I doubt any human could reproduce the moves.
You are right Moonbus.

No human could reproduce the moves.

The reason why you cannot mate with a King and one Knight and indeed two Knights is chivalry.
Knights would deem it beneath them and against their code of honour to attack a lone King.

Add one footsoldier and a lone Knight is up for the fight.

10.  SwissGambit
Caninus Interruptus
25 Jun '13 13:45 / 1 edit
Originally posted by moonbus
This was thought to be impossible until a computer program worked it out. It requires more than 30 moves, however, so, according to tournament rules, this would be a draw. I doubt any human could reproduce the moves.

Wiki has a good article on mate with 2 knights: it is possible if the opposing K is poorly placed.

https://en.wikipedia.org/wiki/Two_knights_endgame#CITEREFSeirawan2003
The article you quoted doesn't agree with your statement.
There are also checkmate positions with the inferior side's king on the edge of the board (instead of the corner), but again they cannot be forced. (my bold)
11.  Paul Leggett
Chess Librarian
25 Jun '13 14:20
Originally posted by SwissGambit
The article you quoted doesn't agree with your statement.
There are also checkmate positions with the inferior side's king on the edge of the board (instead of the corner), but again [b]they cannot be forced. (my bold)
[/b]
Thanks for checking this. I was amazed and doubtful at the same time, and it looks like doubt won.
12.  moonbus
Uber-Nerd
25 Jun '13 16:23 / 3 edits
I vaguely recall an article in an IT journal, not a chess journal, some years ago, claiming that the K+2N vs K problem had been solved. Alas, I can find no reference to this on the Internet. As I recall, the program ran for several days (well over tournament time limit) and the mate required many more moves than the 50-move draw-limit, of which all but the last few moves were not recognizable to humans as having made any progress. I wish I could find that article again... shucks. Anyway, no human could reproduce the sequence, and no tourney director could be expected to adjudicate whether the superior side had made any progress after 50 moves. Given that even Karpov and Annand have landed in K+2N vs K+P endings and made mistakes (drawing in won positions), we mere mortals may accept that K+2N vs K is drawn.
13.  ChessPraxis
Cowboy From Hell
25 Jun '13 17:25
Originally posted by moonbus
I vaguely recall an article in an IT journal, not a chess journal, some years ago, claiming that the K+2N vs K problem had been solved. Alas, I can find no reference to this on the Internet. As I recall, the program ran for several days (well over tournament time limit) and the mate required many more moves than the 50-move draw-limit, of which all but the l ...[text shortened]... nd made mistakes (drawing in won positions), we mere mortals may accept that K+2N vs K is drawn.
Thanks for clarifying your other post.
14.  moonbus
Uber-Nerd
25 Jun '13 17:48
Originally posted by ChessPraxis
Thanks for clarifying your other post.
It is furthermore useful to distinguish impossible, possible, and forced. Checkmate with K+2N vs K is possible, though not forced (for humans within tourney limits), whereas checkmate w/ K+B or K+N vs K is impossible.
15.  SwissGambit
Caninus Interruptus
25 Jun '13 18:48
Originally posted by moonbus
It is furthermore useful to distinguish impossible, possible, and forced. Checkmate with K+2N vs K is possible, though not forced (for humans within tourney limits), whereas checkmate w/ K+B or K+N vs K is impossible.
Wow...when most people put their foot in their mouth, they tend to pull it out at some point...