In double-checks the king has to move!
"double-check" mates
a) White to move and mate in one.
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b) White to move and mate in one.
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c) White to move and mate in two.
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d) White to move and mate in two.
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Solutions: a) R-d8 double check and mate b) NxP(g) or N-c7 double check and mate
c) NxP double check, K-e7 then Q-f7 mate d) N-h6 double check, K-h8 followed by Q-g8 mate
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