Chapter 04 · Beginner · 4 min
Illegal moves
A move is illegal if it leaves your king in check. Even a beautiful idea has to go back to the bench if the king falls.
Explanation
An illegal move is a move that the rules prohibit.
The most important case: you have no right to leave your king in check. You also cannot move a nailed piece if it exposes your king: a nailed piece is a piece that protects something more important behind it. We will see this pattern in detail in the tactics chapter. Same logic for the king: he cannot go to an attacked square.
When a move seems very strong, always check the king's safety. Many brilliant moves suddenly become less brilliant when we notice that the king is captured on the next move. Chess has this little sense of humor.
To remember
A move is illegal if it leaves your king in check or puts your king on an attacked square.
Classic error
Move a piece nailed to the king as if nothing had happened.
Player Tip
Before a spectacular move, always check: is my king staying safe?