Originally posted by David113
What was the first move of the missing white rook?
What was the last move of that rook?
White captured Black's only missing unit on g3. Black made at least 3 captures (Pb2 and c2 plus Bf1 at home).
Black's stuck for legal retractions, so White has to hurry:
-1.Rh5-h1 c7-c6 -2.h2xPg3
Locking his own Rook out, but forced.
-2...g4-g3 -3.Rc5-h5 g5-g4 -4.Nf5-e7 Re7-f7 -5.Kf1-e1
Makes room on the first rank.
-5...Bg6-e8 -6.Ng3-f5 Re8-e7 -7.Kg1-f1 Bf5-g6 -8.Nf1-g3 Qb1-a2 -9.Bd6-f8 Ka2-a3 -10.Rb5-c5 Qe1-b1 -11.Bc5-d6 a3xRb2
The Rook must appear on b2. White's only other missing piece is a Knight, and it alone has the power to escape c2 once Bc1 and Pb2 come back.
To get bK out, Pb2 must come back, which means Bc1 must be at home, which means an R must be in the SE corner. Rb1 is therefore the King Rook, and it's first move was 0-0
, swapping places with wK.