DIAGRAM 8

Interposing the Rook on g2 would not help either as the Queen
would simply take him at the same time checkmating the King.
White's only move is, therefore, to play the King into the
corner, and Black then mates by first taking the Knight and then
moving the Queen to g2 or h2.

Perpetual Check


If a player is able to check the opposing King continually and he
indicates his intention to do so the game is considered a draw.
In the following position, for instance, White on the move can
draw the game by giving a perpetual check on e8 and h5. Black
cannot help himself as he has to go back and forth with the King
on h7 and g8. Without the possibility of this perpetual check
White would be lost, for he cannot prevent the Pawn a2 from
queening and with two Queens against one Black would easily win
as will be seen later from the discussion of elementary endings.


Exchange


To exchange means to capture a hostile man when it allows a man
of the same value to be captured by the opponent.

It is rather confusing that the term "exchange" is also used for