Expert: Tony D'Aloisio - 11/29/2007

Question
Can a king (player A) take an opponent's piece (player B)if the result places the (A)king in check by another (B)piece; which is immobilized because it blocks a check from a third (A)piece?
Player A says the immobile piece is not a check threat because the blocking piece cannot take the king without exposing Player B king to harm. Therefore, the player A king CAN make the move to the otherwise forbidden space.
Player B claims the player A king would be in danger to be taken as soon as the move was made if left in a check position. The player B blocking piece is neither immobile nor harmless, because the game would end before player B king is in danger.
Which rule supercedes: Never leave a king in danger or you cannot move a blocking piece to leave a king in danger or last king standing wins?


Answer
No, the piece cannot be captured if it is protected by another--even if the protecting piece is pinned (the chess term for a piece whose mobility is limited by the actions of another).

Let's take an example--and to do this we shall use algebraic notation (as it's called).  Label the row of squares in front of you a,b,c,d,e,f,g,h from left to right--and number them 1,2,3,4,5,6,7,8 as you move up the board.  Thus the square on your nearest left corner of the board is a1; the square on your right corner is h1.  The square nearest your opponent's left corner is h8, and his right corner is a8.

Place a White King on g6 and a White Rook on a8.  Put a Black King on h8, a Black Bishop on g8 and a Black Knight on f7.  In this position it is illegal for White to capture the Knight with his King due to the fact that the Bishop is protecting it--even though the Bishop is itself pinned to the Black King by the White Rook.  As you suggest, the "last King standing" principle applies.

Also note that this sort of thing can actually decide games.  If White were to attempt the capture of the Knight in a tournament game, he would have to retract the move and come up with another; but in speed (or blitz) chess, if White captures the Knight Black is allowed to capture his King with the Bishop and claim a win as a result.