It is always good to occupy an open file with a Rook.
... 16. K to B sq.
Black cannot play 16. Kt to K 3, because he would thereby leave his K P _en
prise_; he cannot castle, because then his K R P would be _en prise_; and
if he were to return with the Kt to B 3, he would have lost a move.
Therefore he has nothing better than to move his King into safety to B sq.,
and then to Kt 2.
17. Q to Q 2 (?) 17. K to Kt 2
18. P to K R 3 ...
{358}
To prevent Black from playing 18. ... B takes B; Q takes B, Kt to Kt 5,
attacking the Queen.
... 18. Kt to B 3
19. Kt to R 4 19. Q R to Q sq.
Occupying the "open file" and defending the Bishop, so as to free his K Kt,
which was before fixed, as it had to defend the Bishop.