Plain-English Definition
Double check is powerful because captures and blocks usually do not work. The king has to move, which makes calculation more forcing.
Why It Matters
Double check is a calculation shortcut: when it works, the opponent choices shrink fast.
Common Signs in Games
- A discovered check also lets the moving piece check.
- The enemy king has limited squares.
- Blocking one line does not stop both checks.
Common Mistakes
- Treating double check like a normal check.
- Missing the king escape square.
- Choosing a flashy double check over mate.