The King has the simplest move in chess. It can go one square in any direction. The diagram shows the possible moves for both the white King and the black King.
The King plods on the chess board, one square at a time.
Kings are blocked by their own pieces
Just like the other pieces, the King can capture the opponent's pieces but is blocked by pieces of its own color. The diagram shows this for both Kings.
1. How to Castle
a. The King's special move
Once during the game, the King can make a special move. It's purpose is to give the King quick shelter in the corner. Castling is the only situation where you can move two pieces at the same time. The pieces are always the King and one of the Rooks.
There are several restrictions on castling.
The first restriction is that the King and the Rook to be moved are on their initial squares and haven't moved. The diagram shows the ideal case for both Kings and all four Rooks.
How do you know the Kings and Rooks haven't moved and then moved back to their initial squares? If you're playing a game with someone else, you have to remember. Sometimes beginning players forget -- 'You can't castle. You already moved that Rook'! 'No, I didn't'! 'Yes, you did'! 'Prove it'! -- In this diagram, you have to take our word for it.
The second restriction is that the squares between the King and the Rook must be empty. Since the other pieces have all disappeared in the diagram, the condition for castling is met.
b. King two squares toward the Rook which hops over the King
Castling is executed by moving the King two squares toward the Rook, then hopping the Rook over the King. The diagram shows how the pieces end up after castling in the previous diagram. First White has castled to the right. Then Black castled to the right.
c. Castle to either side
This diagram shows the board after both players have castled to the left. There is no rule that both players have to castle on the same side. Sometimes one player castles to the left and the other castles to the right. This is known as 'castling on opposite sides' of the board.
d. King and Rook can't have already moved
In this diagram both players have lost the right to castle. White can't castle, because the King has already moved. Black can't castle because both Rooks have already moved.
e. King can't be under attack
There are other restrictions on castling. You can't castle if your King is under attack. In this diagram, the white Bishop is attacking the black King, so Black can't castle to either side.
f. King can't move through attack
You also can't castle if your King moves through a square that is under attack. In this diagram, the white Bishop is attacking the square to the left of the black King, so Black can't castle in that direction. Black can, of course, still castle to the right.
g. King can't end under attack
You also can't castle if your King ends up on a square that is under attack. In this diagram, the white Bishop is attacking two squares to the left of the black King, so Black can't castle that way. Once again, Black can castle to the right.
h. No restrictions on Rooks regarding attacks
There are two rare situations which are not restricted by the rules. There's no problem if the Rook is under attack just before you castle. It can't be under attack after you castle, because that would mean the King just moved through an attacked square.
If you castle to the left, it also doesn't matter if the Rook moves through a square that is under attack. In this diagram, White can castle to the left or to the right.
2. How to Check, Checkmate, and Stalemate
a. Attack on the King can't be ignored
Check, Checkmate, Stalemate. These chess terms are used in everyday conversation -- here's what they mean.
During a normal game of chess, a player attacks the opponent's pieces many times. Usually the opponent will beat off the attack by moving the attacked piece, by capturing the attacker, or by intersecting the line of the attack. Sometimes a player will ignore an attack on a piece when, for example, there is a counterattack of greater value.
There is one attack that can never be ignored -- an attack on the King. Simply put, you can't leave your King under attack. If you have no way of escaping the attack, you lose the game.
b. Check
In this diagram the white Bishop is attacking the black King. The technical term for this is 'check'. We say that the Bishop is checking the King or that the King is in check.
Now Black must get out of check. This can't be done by moving the King -- the only free square is attacked by the same Bishop; or by capturing the Bishop -- none of Black's pieces attack that piece; which leaves only the possibility of intersecting the line of attack. Black must block the attack with a Knight, a Bishop, or a Queen.
One consequence of this rule is that a player is not allowed to make a move which leaves the King in check. If this happens, the move has to be taken back and another move played.
c. Checkmate
Here the white Rook is attacking the black King. The King can't move -- all the surrounding squares are attacked by a white piece; there are no other pieces available to capture the Rook; and there are no pieces to intersect the line of attack. Black can't get out of check, so it's 'checkmate'. The game is won for White; it's 1-0.
Note that the checkmated King is never captured. The game simply ends at the point where the checkmate is recognized.
A consequence of the checkmate rule is that the two Kings can never be on adjacent squares. That would leave both under attack.
d. Stalemate
This diagram is similar to the previous diagram. All of the squares to which the King might move, as marked by the green circles, are under attack by one of the White pieces. Unlike the previous diagram, the King is not under attack. This situation, where a player has no legal moves and is not in check, is called 'stalemate'. The game is a draw; each player gets 1/2 point.
