It's just a rule, you cannot castle across check or out of check. If you move Bd7, you are no longer being checked and on your next move, IF it makes sense, you could castle (O-O-O). If White moves Qxb7 you still cannot castle, as now you are castling into check. If White moves Qc4 (after you move your B) then, again, you cannot castle, as your King is moving across check (on c8).
Good luck . . .
Castling Queen Side
I just learned apparently you cannot castle during “Check” - I see the responses have been because it’s “such a powerful move” and the comparisons to “en passant”, but I’m confused because it doesn’t break any other rule.
I have not moved my King nor my Rooks and I wanted to castle out of the check. I won’t be in check if I castle, nor will I be in threat of a new check. I will not be “passing” thru a check. I would simply be moving out of check.
Yet it is... illegal? Why?
I see Viktor Korchnoi posed a similar question in 1974. But I have yet to see [in my eyes] a solid reasoning - other than “too powerful”.
Which makes no sense.
Anybody able to lend their opinion as well as facts.
I made this account just to get input from a trusted community - I haven’t played here before but if they’re grandmasters who play, I’d also love their take.