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BDS

Tehtäväniekka, 2017

#2
LEOs a7; h2
PAOs d8, h1; b6, e1
VAO f8

1.LEd7! (2.Bd5#)

1...PAd6 2.LEa4#
1...VAd6 2.LEh7#
1...LEd6 2.Bc2#
1...LEg2 2.PAh4#
1...PAd1 2.PAe1#

After the key d4 is guarded by the wPAd8. The threat interferes with this guard, but reinstates it from the wLEd7. Black defends by interfering with that threatened guard by playing his PAO and VAO to d6. These moves allow the LEO to move off the d8-d4 line, reinstating the guard on d4 by the wPAd8, taking advantage of the mutual interference between the bPA and bVA. These two variations both illustrate the Levmann theme, played out on one single line. That theme is combined with a PAO/VAO Grimshaw. 1...LEd6 corrects against these black errors but unguards c2. 1...LEg2 guards d5, but opens the line to h4. 1...PAd1, which also guards d5, vacates e1 for 2.PAe1#.