Logical Proca retractor in which the foreplan
illegalizes the refutation to the main plan
Black defends by destroying White’s uncastling right!
Main plan: -1.Rf1-f2? (no uncapture duals) any -2.O-O & 1.Rh8#
but -1…d7-d6!
but -1…d7-d6!
Solution: -1.b5xBa6! any -2.Rf1-f2 any (-2…Kg8-f8 -3.~ & Re8#) -3.O-O & 1.Rh8#
The bS cannot prevent uncastling via -1…Sc3-d1 and -2…Se2-c3!
Try: -1.b3xBa4? but -1…/-2…Bb5-a4/d4-d3! and then -3.O-O is illegal.
Retro intention:
The bPs captured all five missing white units, thus neither the bS nor the bK can retract any capture. Notice also that the bK cannot defend by means of a selfcheck on e7/e8/g7. The wPs captured six of the seven missing black units. After -1.Rf1-f2 White can uncastle because the light-squared bB could have been taken by a wP and the missing bP originally on h7 could have been taken by a white officer. However, if Black retracts -1…d7-d6, White loses his uncastling rights (at least at this point): the light-squared bB was taken on its homebase, therefore the wPs had to take the promoted bP originally on h7 which due to the promotion on h1 destroyed White’s uncastling rights (either because White could have never castled or he castled before the promotion took place). If White retracts -1.b5xBa6, (legal move) he still retains his uncastling rights, and what is better, -1…d7-d6 is now illegal because the promoted bB could have never left h1.
