09-21

The Berlin theme doubled: once realized, once preventively avoided
Berlin theme (New German Logic): a mainplan by White forces Black to mate him as Black’s unique
defense. After a foreplan, the mating move is downgraded to a mere check.



Try (main plan): 1.b6? (thr. 2.b7#) Rf5#! Berlin-mate-1
Try: 1.Rxh5 Bxh5 2.b6? Rf5+ 3.Ka4 Bd1+ 4.Rc2 Bxc2#! Berlin-mate-2
Solution:
Foreplan-1: 1.Rxh5 Bxh5
Foreplan-2: 2.Rc2 (thr. 3.Rc7 4.Sb6#) Sxc2 (Berlin-mate-2 preventively avoided)
Main plan: 3.b6 Rf5+ (Berlin-mate-1 downgraded) 4.Ka4 Rb5/a5+ 5.Kxb5/a5 6.b7# model mate.