Tactical motifs
Double check
Two pieces give check at once — the king is forced to move.
What is the double check?
A double check is a special discovered attack where both the moving piece and the unveiled piece give check at the same time. You cannot block two checks or capture two checkers in one move, so the king is forced to step away — nothing else is legal.
Why the double check matters
It is the most forcing move in all of chess. No matter how many defenders surround the king, a double check ignores them and drags the king into the open. That is exactly why so many famous mating combinations are built on it.
How to use it to win
Set up a piece in front of a long-range attacker so moving it gives check while the attacker behind also checks. Since the king must move, you can often follow with a decisive capture or a smothered/back-rank finish.
A concrete example
Réti–Tartakower's miniature ends with a double check that herds the king straight into mate — a one-line classic worth memorising.
Try an example puzzle
A real double check puzzle from the app. White to move — find the idea, then reveal the line.
7 
2 a 
g Show solution
1. Re8#
Drill the double check on thousands of real puzzles, matched to your rating.