If my opponent only has the king, and I have two knights and the king, can I win?

no its impossible

not if your opponent makes the correct moves. but if he doesn't know how to play it, or wants to get mated, you can checkmate with 2 knights :)

Thanks for the feedback!

 

if king is in corner is works

What might be interesting to know for you is that with K+2N against the bare king you usually can't force mate, but this assessment changes completely if your opponent has got a last pawn. Provided it has not yet advanced too far, you can force the king into the corner and then, just in the moment where a stalemate would draw the game, release the pawn to redirect the blockading knight to deliver mate, sometimes exactly in the moment that pawn queens.

This process is quite complicated and in some cases requires more than fifty moves, which is, as I believe I remember, why in some theoretical positions the fifty-move-rule has been exteneded to something like 75 moves.

I think the rules as they stand say that 50 moves is a draw even if a mate could be forced in more than 50 moves.  I believe it used to be different. 

looks like i was wrong. . . .

it works but is hard to force king into it.

You can checkmate with two knights, but it is very hard! 

   Checkmating with two bishops is a lot easier to do!

   

  Good luck!

Against a bare king it is impossible to force mate (the side with the solitray can walk into it if suicidal.)

Troitsky and Cheron made incredible studies of 2 Knights vs Pawn, and according to Muller and Lamprecht in "Fundamental Chess Endings", the longest such task takes 115 moves!

According to Wikipedia (buyer beware), FIDE had at one time adjusted the 50-move draw rule to allow 100 moves for such positions, then down to 75 moves, and finally back to the original 50 moves.

The rarity of the 2 Knights vs pawn questions the value of studying this material...except for the pure logic invoved.

As posted earlier, 3 Knights vs King can force mate. Fine is the only author I recall covering this, but there may be others.

It's IMPOSSIBLE to force the king into it, unless he's already almost in checkmate, like in the example that appears to have been deleted...  K vs K+2N is a draw except for very specific positions where the king is almost in checkmate, just like K+R vs K+R is a draw, except for specific obvious positions where one of the rooks can be won.

 

True you need a cooperative opponent

You have to read greatest Chess Composer Troitskiy! 

He made it much clever, generally...

Why do some people post nonsense in this thread?  Under normal conditions - It is not HARD - it is IMPOSSIBLE to force a King into a mate with 2 Knights.

I think that the original question has been answered thoroughly. 

An interesting aside, though, is the three-knight mate.  The third knight makes it possible, and once in a league match, I did it with four knights, which is almost easy to do.  Try it out sometime, on yourself or a computer. 

I accidentally deleted a precious post, leaving a response an orphan. Here it is updated: [say white has K+N+N, Black has lone K]

Even with black cooperating, it is well knnown that black can only be mated with his K in a corner (the position 1 and its symmetries): so what about position 2?

position 1:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

pos ition 2:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answer: position 2 is unattainable however badly Black plays! White is on move, so what was the last move i.e. what did black move to reach this position? No possible answer.

 

 

 

Isn't it possible?

 

just fyi the '50 move rule' for draws is 50 moves without a capture or a pawn move. so if they have a pawn on the board, chances are they'll move it and reset the moveclock back to zero, giving you 50 more chances to work with whatever you have.

Only possible with a bit of cooperation and experience from the knight's players.
I try never to end up with two minor pieces. Bishops are annoying for a mate too.

Try preserving your pawns(if you have any). In an empty board situation one pawn might well be worth much more than 2 knights.