Double Check in Chess
Double check is the most powerful tactical weapon in chess: two pieces give check simultaneously. The opponent cannot block both checks, cannot capture both checking pieces, the only legal response is to move the king. This makes double check the most forcing move possible.
How double check works
A double check occurs when a piece moves, creating a discovered check, AND the moving piece also gives check. Now two pieces check the king: blocking one still leaves the other check. Capturing one leaves the other. Only moving the king resolves both.
Why it's so deadly
Because only the king can move, the attacker has enormous control over where the king goes. Many of the most famous mating combinations in history end with a double check forcing the king into a mating net. Double checks often appear in attacking games from the legends database.
Training
Solve double-check puzzles. Look for positions where a discovered check can also deliver a second check with the moving piece.