🕸📝Fergus Duniho wrote on Sun, Sep 16, 2018 01:03 PM UTC:
After White's pawn takes the Queen and promotes to an Archbishop, Black has only four moves available. Two of these moves would expose it to capture without any significant consequence for White, and another would allow White to move the Archbishop to b8. The remaining move is to go to d7, checking the King. If White responds by taking the checking piece with either Archbishop, the resulting position is a stalemate. If White responds by moving the King, Black can take either Archbishop en prise. If White responds with a block on e6 from the Archbishop on e6, Black can exchange Archbishops. This might still be favorable for White. If Black takes the Pawn at b5 instead, White can still probably force an advantage. So, it looks like White could still win if the Pawn promotes to an Archbishop. The advantage of promoting to a Bishop is that White can win quickly and decisively. If the Archbishop moves to d7 for check, the Bishop can take it without causing stalemate. If the Archbishop makes its only safe move to c7, then the Bishop can safely check the King from b7, forcing the King to move to b8. The Archbishop can then move to d7 for checkmate.
After White's pawn takes the Queen and promotes to an Archbishop, Black has only four moves available. Two of these moves would expose it to capture without any significant consequence for White, and another would allow White to move the Archbishop to b8. The remaining move is to go to d7, checking the King. If White responds by taking the checking piece with either Archbishop, the resulting position is a stalemate. If White responds by moving the King, Black can take either Archbishop en prise. If White responds with a block on e6 from the Archbishop on e6, Black can exchange Archbishops. This might still be favorable for White. If Black takes the Pawn at b5 instead, White can still probably force an advantage. So, it looks like White could still win if the Pawn promotes to an Archbishop. The advantage of promoting to a Bishop is that White can win quickly and decisively. If the Archbishop moves to d7 for check, the Bishop can take it without causing stalemate. If the Archbishop makes its only safe move to c7, then the Bishop can safely check the King from b7, forcing the King to move to b8. The Archbishop can then move to d7 for checkmate.