Two knights endgame

The two knights endgame is a chess endgame with a king and two knights versus a king, possibly with some other material. The material with the defending king is usually one pawn, but some positions studied involve additional pawns or other pieces. In contrast to a king plus two bishops (on opposite-colored squares), or a bishop and a knight, a king and two knights cannot force checkmate against a lone king. (However, the superior side can force stalemate.) Although there are checkmate positions, the superior side cannot force them against proper (and easy) defense (Speelman, Tisdall & Wade 1993:11).

On the other hand, if the weaker side also has material, checkmate is sometimes possible.(Troitzky 2006:197–257) The winning chances with two knights are insignificant except against a few pawns. (Haworth, Guy M^cC (2009). "Western Chess:Endgame Data". CentAUR. ) These positions were studied extensively by A. A. Troitsky. (See Troitsky line.) With a single pawn the technique (when it is possible) is to block the pawn with one knight and use the king and other knight to force the opposing king into a corner or near the other knight. Then when the block on the pawn is removed, the knight can be used to checkmate (Dvoretsky 2006:280).

Although there are checkmate positions with two knights against a king, they cannot be forced. Edmar Mednis stated that this inability to force checkmate is "one of the great injustices of chess" (Mednis 1996:40).

...
Wikipedia