[Retros] shortest proofgames of castling switchback

[Hirokaz ONODA]

Hi Andrew,

Thank you for your pointing it out. And very very sorry for my having
missed it out.

Now, here we have:

The shortest PG for castling switchback:
(7.5, 1) 1.e4 f5 2.Bc4 f4 3.Ne2 f3 4.0-0 fxe2 5.f3 e1=R 6.Kf2 Re3 7.Rh1 Rd3
8.Ke1 (Joost de Heer, 2005.2.10)

Without promotion, against an attacking Queen:
(7.5, 5) 1.e3 d6 2.Bb5 Qd7 3.Ne2 Qxb5 4.0-0 Qxe2 5.f3 Qxd1 6.Kf2 Qxc1 7.Rh1
Qe1 8.Kxe1  (Andrew Buchanan, 2005.2.11)
 
Without promotion, against an attacking Knight:
(8.5, 2) 1.g3 f5 2.Bh3 f4 3.Bxd7 Nxd7 4.Nh3 Ne5 5.O-O Nf3 6.Kg2 e5 7.Rh1
Ng1 8.Kf1 f3 9. Ke1 (Ayako Okaya, Problem Paradise 13, 1999)

Captureless: vacant

Q-side castling switchback: vacant
cf.(after O-O-O, K returns, but R does not):
1.d4 c5 2.Bh6 cxd4 3.Qxd4 Nxh6 4.Nd2 Nf5 5.0-0-0 Nxd4 6.Re1 Nxc2 7.Kd1 Nxe1
8.Kxe1 (Christoph Fieberg, 2005)

Castling switchback for both sides: 
r1bnk2r/pp1p2pp/2n2p2/2bQp3/4Pr2/5PR1/PP1P2PP/RNB1K2R
SPG 19.0 14+15 C+
(Andrei Frolkin 2nd Prize Die Schwalbe 1990)

 
Amici Sumus,
Hiro


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