Over the years, I have loosely classified Jerome Gambit games by strategy: "White attacks aggressively", "Black counter-attacks aggressively", and "Black counters well, so White adopts a slow, solid, come-get-me approach". That covers a lot of games in The Database.
Then there are games like the following, however, which might as well be classified as "somewhere over the rainbow".
Wall, Bill - Guest4105968
PlayChess.com, 2018
1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.Bxf7+
4...Kxf7 5. Nxe5+ Ke6
The move appears in 28 games in The Database (updated). It is somewhat understood, after some serious blog coverage, here - the most recent being in another of Bill Wall's games from 2 years ago (see "Jerome Gambit: This Is How It's Done"), where I wrote
This move follows the "psychology" of "If you want me to take the Knight, then I won't take the Knight", but it is simply not a good move. It is relatively rare: The Database has 24 games, with White scoring 65% .
Still, it is worth knowing the followup, as this "defense" has shown up in the games of Jerome Gambit regulars: blackburne, MrJoker, Petasluk, stretto, UNPREDICTABLE, and ZahariSokolov. I have faced it a couple of times and come away with wins.
In fact, I have posted a disproportionate number of times on the line - although, in fairness, they were all interesting posts, going back to "You, too, can add to Jerome Gambit theory" and including "A Strange, But Intriguing Path, Parts 1, 2, & 3" and "Still Strange, Still Intriguing Parts 1, 2, 3 & 4." The most recent post on the line is "We Know What We're Doing (Sort of)".
Curiously enough, there is still more to learn about the variation, as we shall see.
6.Qg4+
This move, Stockfish 9's preference, is probably the best move, although it has appeared only 5 times in The Database before the current game.
Actually, computer analysis is only slightly helpful in choosing the proper move. Some examples are: 6.d4, evaluated as 0.00 by Stockfish 9 at 35 ply, is seen as the second best move; while the retrograde 6.Nf3!? (no games in The Database), evaluated as -.28 by Stockfish 9 at 35 ply, is seen as the third best move.
Certainly 6.0-0 (no games in The Database) should be playable, although Stockfish 9 at 35 ply evaluates it as -.65 - what's 2/3 of a pawn between friends, right? The game should continue 6...Nxe5 (the only move for advantage) 7.d4 d6.
Most popular for White, and probably most thematic, has been 6.Nxc6, which Stockfish 9 evaluates (at 35 ply) as -.81 after 6...dxc6. A mistake is 6...bxc6?, as it is strongly met by 7.Qg4+!. Black can mix everything up by not capturing the Knight and playing, instead, 6...Qh4!? although Stockfish 9 rates the position after 7.Qe2, then, as roughly even, +.10 (at 35 ply).
With Stockfish 9 pontificating as usual, it is important to remember that we are usually talking about games between club players, and Geoff Chandler's humorous but accurate blunder table always needs to be taken into account - especially because we are talking about the Jerome Gambit! Play what you feel comfortable playing.
6... Kxe5 7.d4+! Bxd4 8.Bf4+! Kf6 9.Bg5+! Kf7 10.Bxd8 Nxd8
Okay, White has played the "best" moves, and now has a Queen and a pawn for three pieces. As Dorothy said, in "The Wizard of Oz", "Toto, I've a feeling we're not in Kansas anymore."
Indeed, the position looks like a challenge to play. Nobody is going to attack or counter-attack aggressively, and it looks like it would be to White's disadvantage to sit back and do nothing.
(By the way, the snarky 10...Bxb2?!, instead of capturing the Knight at d8, would be met by 11.Qf3+! Ke8 12.Bxc7, when, after 12...Bxa1 13.Na3, White would have an advantage in development and King safety to offset the material imbalance [Q + P vs R + B + N]. White can respond to either 13...d5 or 13...Nf6 with 14.0-0 and Black will not be able to get his defenders out fast enough, as they will also have to run the risk of going to the wrong square and being picked off by the enemy Queen with a checking fork. This is a return to the Jerome theme of "White attacks aggressively".)
Looking for guidance, I discovered that the venerable Basic Chess Endings by Reuben Fine (1941) has about 1/4 of a page covering "QUEEN vs THREE PIECES", which can easily be summarized
Without Pawns this is drawn, but there are a few positions where the pieces win... With Pawns the two forces are roughly equivalent. However, with no other material Q + P vs 3 pieces is drawn, while 3 pieces + Pawn win vs Queen.
The newer Fundamental Chess Endings (2001) by Karsetn Mueller and Frank Lamprecht has about a page of coverage, devoted to the analysis of two game examples, and the terse bit of advice
Outposts, king security and passed pawns again play a major role
I then checked out the internet to see what was available. One such article that I found to be helpful is here.
All of this information is enlightening, but, in the meantime, two people were playing the game.
[to be continued]