not necessarily because the dark squared bishop can be a useful defensive piece for Black in the King's Indian. Its exchange can leave Black in trouble.

A lot of what was going on has to do with a typical KID battle of the c5 square. If Black can plant a N safely there its a good advantage, as seen in this game.

Petrosian takes the first chance he gets with 8...Nc5. White chooses to protect the e-pawn under double Knight attack with 9. Nb2 which gives Black time to protect the lead N with 9...a5.

So White plays 10.Qc2 to protect the e-pawn and free the N to challenge c5 square.

10...Bh6 wasn't taken lightly but it does get rid of a c5 threat either way N or B. It does weaken Black's Kside but it appears White's on the defense so it's probably worth it.

After 11...Bxc1, 12. Raxc1 lets Black defend c5 with 12...Nfd7. Then Black eliminates the other threat to c5 and ends up posting a N there with tempo against the Queen anyway.

<XVIII первенство ссср по шахматам - <С. Флор--Т. Петросян> (R9) G-81 p163>

A fuller ref to Pachman would have saved me a little time - given I was flipping through, page by page, trying to find the Flohr game. (It wasn't in the game index.)

A bit tedious, so I soondecided to do a google search - which yielded the source directly!

https://books.google.com/books?id=B...

Oh the irony! (aka OCR wins again)

<ziryab>'s ref comes from a note in <Sakellarpoulos--Boleslavski (Helsinki 1952) p18> for 10...B-R3!! (a bit exuberant) concerning good vs bad bishops. And yes, Pachman seems to suggest Flohr played 12.Nxc5.

Perhaps in a different game with Petrosian (given no particulars of the sidenote game is given other than the players)?

Let's do a tree search with SCID to see...

OK, it seems Pachman got it wrong. The earliest KID with this position:

click for larger view

is <Petrosian--Geller (Moscow 1949)>, according to <Millbase>.

Petrosian was the one to play 12.Nxc5, next year, Flohr played 12.Raxc1 for the first time.

Side note: 12.Raxc1 seems more natural to me, and is far and away the dominant continuation in <Millbase>. But analysis seems to suggest (in agreement with Pachman(?)), that White has full flexibility to take with either rook, or to even play as Petrosian did in 1949.