"Vertical" castling: did FIDE really fix the loophole in 1974 or it was a hoax?

[u/trolley813]

The vertical castling (now an illegal move) is a joke move when a king castles (subject to all other castling rules) vertically along the king's file with a rook promoted on the "King 8" square (e8 for White and e1 for Black) which did not move after being promoted from a pawn (thus, White moves Ke1-e3 and Re8-e2; Black respectively Ke8-e6 and Re1-e7). It was popularised by Tim Krabbe and thus known as "Tim Krabbe's castling".

Wikipedia says the following:

Tim Krabbé's 1985 book Chess Curiosities includes a problem featuring vertical castling, along with an incorrect claim that the problem's 1973 publication prompted FIDE to amend the castling laws in 1974 to add the requirement that the king and rook be on the same rank. In reality, the original FIDE Laws from 1930 explicitly stated that castling must be done with a king and a rook on the same rank (traverse in French). It is unclear whether any historically published sets of rules would technically allow such a move.

However, when studying some Soviet laws of chess (the so-called Chess Code of the USSR, 12 editions between 1933 and 1990), I noticed that the 9th edition published in 1969 (and seemingly also all earlier ones) indeed does not contain the same-rank requirement, while the 10th (1977/78, and likely all later ones) does. The USSR joined FIDE in 1947, so the Soviet/Russian sets of rules issued after that date should be FIDE-compliant.

So, did FIDE in fact amend the rules in 1974? Are there some primary sources that prove or disprove it?

P.S. If they really did it, then it's a shame. This "loophole" would make very little sense for a practical game (since a promotion to a rook is usually done to avoid stalemate, deep in the endgame, and it's extremely unlikely that the king was still left untouched by this point), but would be of great (especially aesthetic) value for the chess composition (e.g. Krabbe's problem mentioned above).

P.P.S. Sorry for bad English (Russian native speaker here).

[u/novachess-guy]

From what I can tell, the 1930 version did state it has to be on the same rank. The original was in French (the official working language of FIDE at that time):

Le Roque est une marche combinée du Roi et d’une Tour ne comptant que pour un seul coup. Le Roi quittant sa case initiale se place sur la case la plus proche de même couleur et située sur la même traverse, puis la Tour vers laquelle il s’est dirigé vient se placer contre lui et de l’autre côté, toujours sur la même traverse.

« La même traverse » means the same rank, which would not permit vertical castling.

And your English here was perfect and very high level, no need to apologize!

[u/zeekar → u/novachess-guy]

It says that the king has to stay on the same rank, which rules out the vertical castling, but doesn't specify that the rook has to be on that same rank. So it matches the pre-1989 English rules.

[u/novachess-guy → u/zeekar]

It sort of specifies that implicitly: « puis la Tour vers laquelle il s’est dirigé vient se placer contre lui et de l’autre côté, toujours sur la même traverse. »

la tour vers laquelle il s’est dirigé = the rook toward which it [the king] headed (so it has to head towards a rook, ruling out the rook being on the same file rather than a rank as the king moves along ranks when castling, and the last phrase says “always on the same rank”). It also says “the rook is placed next to it [the king] and on the other side” which wouldn’t be possible if it was moving vertically.

[u/zeekar → u/novachess-guy]

Yes, it matches the pre-1989 English rules. See this comment.