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a b c d e f g h
8 a8 b8 rd c8 d8 e8 f8 g8 h8 rd 8
7 a7 pd b7 pd c7 d7 ql e7 nd f7 kd g7 pd h7 pd 7
6 a6 b6 c6 d6 e6 f6 g6 h6 6
5 a5 b5 c5 d5 e5 f5 g5 bl h5 5
4 a4 b4 c4 pl d4 e4 f4 g4 h4 bd 4
3 a3 b3 c3 d3 e3 f3 g3 h3 nl 3
2 a2 pl b2 qd c2 d2 e2 pl f2 nd g2 pl h2 2
1 a1 b1 c1 d1 rl e1 kl f1 bl g1 h1 rl 1
a b c d e f g h
1...Nd3# is checkmate.
Though the knight can be captured
3 different ways, but the bishop
on h4 is also checking the white king.
White king has no safe square to go.
This is an example of double check and checkmate.

Double check is a check delivered by two pieces simultaneously. It is one of the most powerful tactics in chess. Because the opponent cannot capture both attackers in one move, the only way for a king to escape double check is to move to another space. In a game situation, double check is always the result of a discovered check.