When you Attack the King When you make a move that puts your opponent's King in danger of being captured, you tell your opponent you're attacking their King by saying "Check." Your opponent must then make a move that protects their King. If they can't make such a move, then you win the game.

Why? The moving player says "Check" as a polite way of telling their opponent that they have to protect their King on their next move. Index | Next: An Example of Check