// Find the squares that opponent attacks in our king flank, and the squares
// which are attacked twice in that flank but not defended by our pawns.
kingFlank = KingFlank[file_of(ksq)];
b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;
// Find the squares that opponent attacks in our king flank, and the squares
// which are attacked twice in that flank but not defended by our pawns.
kingFlank = KingFlank[file_of(ksq)];
b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;