What Makes a Draw? Part Two
By Grandmaster Alex Yermolinsky
What Makes a Draw?
50 Move Rule and Repetition of Moves
The most frustrating example of a drawn ending is having a King plus two Knights vs. the lone enemy King. At first glance White has a large advantage, +6 points if you count the piece value, and he won’t have much trouble driving the black king to the side of the board. However, White then discovers that mate is only possible if the opponent makes a mistake.
If Black makes the right moves, there’s no checkmate to be found for white. Then what? Will the players keep pushing pieces around until next Christmas? The rulebooks have special ideas to prevent that from happening...
If one side has an undisputed advantage, but he or she is unable to push that advantage home to checkmate, the game will eventually be called a draw after 50 moves of no progress. Progress is defined as either a capture (taking an enemy piece) or a pawn push.
Positions such as Rook vs. Knight or Rook vs. Bishop can't be won by force, and so the game will only be allowed to continue until the attacker gives up trying and offers a draw, or the 50 Move Rule Draw is claimed. Obviously, to back up this claim the player has to produce a readable and complete game scoresheet (which is why you MUST learn to keep notation of your games) 
. The 50-move rule may save you a draw even in a theoretically lost position if your opponent is unable to checkmate, such is often the case in the notoriously difficult King+Bishop+Knight vs. King ending...
Most "untitled" (meaning anyone below Master level) players haven't studied this ending, so if you find yourself on the defensive side, don't give up!!
In the recent South Dakota State Scholastic Championship one of the decisive games in the K-3 section came down to a King+Rook vs. ingending. The girl with the rook was close to checkmating her opponent a few times, but she kept on missing her chances.
In the end White ran out of moves, and the game was called drawn based on the 50-Move Rule.
Sometimes a situation appears on the board in which both players must repeat moves because other options would make their positions worse, or even lead to a forced loss of the game.
The above position keeps on repeating itself, and once it happens three times always with the same side’s turn to move, one of the players may call the arbiter and demand a draw by the Three-Fold Repetition. Once again, a correct game scoresheet needs to be produced to make the claim valid.
To learn more about draws, follow onto Perpetual Check and Stalemate.