|g15713: E. 1.0
Black to move after White played 68. Qxd2
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Rediscovered extremely rare and unusual ending - Q + B vs. R + R
with no pawns on the board. John Nunn extensively analyzed the above diagram in his masterpiece <Secrets of Pawnless Endings>.
Syzygy says it is a tablebase win for White -
"Queen and a minor piece versus two rooks: this is usually a draw for a knight and a win for a bishop, although the win takes up to eighty-five moves. The best method of defense is to double the rooks on the third rank with the opposing king on the other side and keep the king behind the rooks. This case with a bishop and queen versus rooks is unusual in that such a small material advantage forces a win. It was thought to be a draw by human analysis, but computer analysis revealed a long forced win."
Going back to diagram E. 1.0
Here is a tantalizing taste of what can be found in an excerpt from John Nunn's book:
<"The ending of"> ♕ + ♗ versus ♖ + ♖ <"is generally won, but it is by no means easy. In this position Black has already set up the basic defence, which involves doubling up his rooks on the third rank. This 'third-rank defence' is quite resilient, and can only be broken down by rather subtle manoeuvers. White's first task is to activate his queen and bishop, and drive Black's king onto the back rank. Then White can try to force his king towards the key central square e5.">
<"It is worth noting that two rooks are easily capable of giving perpetual check, so it is important that White's bishop retains control of e6. If Black were to check on g6, then he would only impel White's king towards the target square e5.">
To see the rest of his great analysis - buy his book!
68...Rcd6 69.Qc3 Kf8 70.Qc8+ Ke7 71.Qc7+ Ke8 72.Bc4 Kf8 73.Kg3 Rg6+ 74.Kf4 Rgf6+ 75.Ke5
Black to move
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White has accomplished his goal(s) of:
(1) first task is to activate his queen and bishop
(2) second task is to drive Black's king onto the back rank
(3) third task is having his king go towards the key central square e5
<"Now Black is placed in immediate zugzwang.">
75...Ke8 76.Bb5+ Kf8 77.Qc8+ Kg7 78.Bc4 Kg6 79.Qg4+ Kh6 80.Bf7 Rb6 81.Qg8 Rg6 82.Bxg6 Rxg6 83.Qd8 Kg7 84.Kf5 Kh7 85.Qe8 Rg7 86.Kf6 Rg1 87.Qd7+ Kh8 88.Qc8+ 1-0
<"An extremely instructive ending which was very well conducted by White.">
Reference: Nunn, John (2002), <Secrets of Pawnless Endings>
2nd edition., pages 367-370
Gambit Publications, ISBN 1-901983-65-X
Note: one wants the second edition which has 62 pages of extra material covering 6-man endgames.
centre and defence are chiefly British spelling variants of center and defense respectively
In American English, maneuver is the standard spelling while manoeuvre is the preferred spelling throughout the rest of the English-speaking world.