Yes. Though I don't know right off if they can force it without their own king's assistance.
Can 3 knights mate a king
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Jun 10, 2016
0
#5
wanmokewan wrote:
I think it can be forced.
Do you mean without the king helping? I know three knights can mate just don't know if the king has to protect one of the knights at some point.
Guess I could verify with a tablebase. 
Jun 10, 2016
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#7
It can definetely be forced.
Check out this game between two Stockfish engines.
From Yuri Balashov and Eduard Prandstetter. 1992. Basic Endgames. p.66.
Jun 10, 2016
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#10
It seems like three knights are fairly strong and will nearly always mate a lone king. The tablebases show they will also generally win against a single knight (longest mate 90 moves) and against a single bishop (longest mate 96 moves). Of course there are plenty of drawn positions in both cases.
http://www.chessgames.com/perl/chessplayer?pid=10156&kpage=1 First comment.
Jun 11, 2016
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#12
The question that comes to my mind is can the bare king be ++'d if not in the corner ?
IOW's, can a position like this be rewound and re-created ?
Jun 11, 2016
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#13
The_Ghostess_Lola wrote:
The question that comes to my mind is can the bare king be ++'d if not in the corner ?
IOW's, can a position like this be rewound and re-created ?
I don't think that particular one could be. The knight on f4 couldn't have been in a positon where black would have been forced to that square.
Jun 11, 2016
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#15
actually 2 knights can mate too, even in real game, but sure in case of opponent's blunder
Certainly (with king's help). An old (80+ years) endgame puzzle was 2knights&king, against King&pawn. Supposedly, one knight blocks the pawn, while the king&knight drive the other king into the corner. Then blocking knight wanders over to deliver the mate, while the pawn marches to the eighth. All I ever saw was the last seven moves with the black pawn blocked on a7. The final moves were clear, but I never was convinced that the black king could be driven to the corner in the first place.
It takes four knights to mate without the king's assistance. I havent tried with three knights. But I've found so far that any combination of four minor pieces can give checkmate. Again, without any king on the board, which I assume is what the OP was talking about.
Jun 11, 2016
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#18
It's impossible to find this in a real game!
The endgame K+N+N vs K+pawn is VERY HARD.
wayne_thomas wrote:
From Yuri Balashov and Eduard Prandstetter. 1992. Basic Endgames. p.66.
a good find, thx for sharing
Jun 11, 2016
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#20
xman720 wrote:
It takes four knights to mate without the king's assistance. I havent tried with three knights. But I've found so far that any combination of four minor pieces can give checkmate. Again, without any king on the board, which I assume is what the OP was talking about.
Nalimov tablebases show that it is indeed possible with 3 knights. In the position I set up, similar to post 7, the king didn't have to take part, but could have.
I have no idea