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Twin Problem 5: Mate in 2 Moves

(White: Ke1, Ra1, Rf2, Nb1, Ba7, Bb7, b3, d2, Black: Kg1, Rd4, Bh7, e4.)

White to move and mate in 2

Now, rotate the board quarter turn anti-clockwise:

(White: Kh5, Rg6, Rh1, Nh2, Bb1, Bb2, f2, g4, Black: Kh7, Re4, Bb8, e5.)

White to move and mate in 2

Solution:

(a) 1. Nc3! Rb4 2. O-O-O# (2. Ke2#) 
(b) 1. Kg5 Rxg4+ 2. Nxg4# (1. ... Re3 2. Nf3#, 1. ... Re1 2. Nf1#)