The Short Answer: No, Never
In chess, a King can NEVER capture another King.
Furthermore, two Kings can never stand next to each other on the board. There must always be at least one empty square separating them—whether horizontally, vertically, or diagonally.
Illegal Touch: Legal Separation:
. . . . . . . . . .
. . ♚ . . . . ♚ . .
. . ♔ . . ❌ ILLEGAL . . . . . ✅ LEGAL (1 square gap)
. . . . . . . ♔ . .Why Is It Illegal? (The Logic of Check)
The reason a King cannot take a King is rooted in the most fundamental rule of chess:
FIDE Rule 3.9: A player is never allowed to make a move that exposes their own King to check, or leaves their King in check.
Here is what happens if you try to take the enemy King:
- Every King attacks all 8 squares in a 1-square radius around itself.
- If White’s King moves to touch Black’s King, White’s King is stepping directly into the attack zone of Black’s King.
- Because stepping into check is illegal, the move is rejected as an illegal move.
- In tournament chess, making an illegal move incurs a time penalty; two illegal moves result in forfeiting the match.
The Concept of Opposition
Because Kings cannot touch, they create an invisible barrier between them. When two Kings stand on the same file or rank with exactly one square between them, this is called The Opposition:
White King on e4 <--- [e5 Buffer Square] ---> Black King on e6Neither King can advance forward onto the buffer square (e5). The player who does not have to move is said to “hold the opposition,” forcing the opposing King to give ground and step aside.
What Happens When Only Two Kings Are Left?
If all other pieces and pawns have been traded off and only the two bare Kings remain:
- Neither player has the firepower to deliver checkmate.
- The game terminates immediately in a draw due to Insufficient Material (FIDE Rule 5.2.b).
- You do not need to play 50 moves; the arbiter or chess server stops the game instantly and declares a tie (½ - ½).
