H.R.H. the Duke of Brunswick is a thorough devotee to Caissa; we never saw him but he was playing chess with some one or other. We were frequent visitors to his box at the Italian Opera; he had got a chess-board even there, and played throughout the performance. On our first visit "Norma" was performed. The Duke's box is right on the stage; so close, indeed, that you might kiss the prima donna without any trouble. Morphy sat with his back to the stage, and the Duke and Count Isouard facing him. Now it must not be supposed that he was comfortable.A casual reader of Frederick Edge's Paul Morphy, could easily surmise from this passage that Vincenzo Bellini's Norma was performed on stage when Paul Morphy played his "most famous game".* However, David Lawson, who researched matters thoroughly, asserts that the game was played during a performance of Barber of Seville by Gioachino Rossini.
Frederick Milnes Edge, Paul Morphy: the Chess Champion (1859), 172.
On the second of November they heard the Barber of Seville, during which Morphy played his most famous game, the Duke again consulting with Count Isouard. In his games with Morphy, the Duke always had a partner, sometimes two, Counts Isouard and Casabianca consulting against him.Lawson's documentation is not on par with his research. Verifying his claims, and the counter-claims of many writers before him, has proven vexing. Edward Winter's outline of several unknown details and the contours of disagreement is well-worth reading (citation below).
Lawson, Paul Morphy: the Pride and Sorrow of Chess (2010), loc. 3271 Kindle ed.
It seems clear from these two passages in the books by Edge and Lawson that Morphy played several games against the Duke of Brunswick in consultation with one or more Counts. Several of these games were played at the opera as a guest of the Duke. Yet, it seems, only one record of these games remain.
This one recorded game was a stellar performance by Morphy. It is included by Rashid Ziyatdinov in GM-RAM: Essential Grandmaster Knowledge as game 14. It was my study game a week ago, and this past week comprised my "lesson of the week" for youth chess players. It is an instructive illustration of effective and ineffective pins. My annotations were written without sight of a chess board, giving me confidence that I am beginning to understand this game.
Morphy,Paul -- Duke of Brunswick, Count Isouard [C41]
1.e4 e5 2.Nf3 d6 3.d4 Bg4
The inadvisability of this pin is addressed in "Lasker's Rules".
Black to move
The rapid conclusion of this game may give the impression that the Duke and Count were weak chess players. But, here, they demonstrate understanding of zwischenzug--something many of my young chess students need to learn.
The immediate 4...dxe5 loses a pawn.
4...Bxf3 5.Qxf3 dxe5 6.Bc4
This simple checkmate threat is far too effective against scholastic players. Even at the Washington State Elementary Chess Championship, games will end quickly with Scholar's Checkmate.
The Duke and Count block access of White's queen to f7.
Morphy renews the threat against f7, adding an attack on b7. From b7, the queen may snatch the rook.
Black to move
Thinking that many of my students could quickly find the answer, I asked: How can Black protect both the pawn on f7 and the rook on a8? I was disappointed at the answers.
8.Qxb7 Qb4+ 9.Qxb4 Bxb4+ 10.c3
Morphy's pin of the king's knight is vastly more effective that when his knight was pinned, although he, too, violates the letter of Lasker's Rule.
9...Nbd7 seems better.
White to move
10.Nxb5! cxb5 11.Bxb5+ Nbd7
White to move
Morphy has managed to pin both of Black's knights.
Both White rooks will come to d1 for the battle of d7.
It was important to capture with the rook, temporarily sacrificing an exchange when already down material, because this capture keeps a Black piece pinned on d7.
Rxd7 14.Rd1 Qe6
White to move
White is down a rook for two pawns, and yet has more force in the battle. If Black is able to mobilize their bishop and other rook, this game will become one of Morphy's rare losses.
15.Bxd7+ Nxd7 16.Qb8+
Forcing Black's response and leading to checkmate. This queen sacrifice is the essence of the Opera Checkmate, a combination that leads to a more elementary bishop and rook checkmate.
16...Nxb8 17.Rd8# 1–0
*Frank Marshall called Morphy's opera game, "the most famous game of all time" (Comparative Chess ). See Edward Winter, "Morphy v the Duke and Count," Chess Notes (updated 20 March 2014).