White: AndyAndyO - thematic tournament, ChessWorld.net, 2019
Olaf Ulvestad was a US master and openings theoretician, now known primarily for his variation of the Two Knights Defence: 4 Ng5 d5 5 exd5 b5!?. Ulvestad wrote enthusiastically about his discovery in the 1941 issues of Chess Review: “It stands out head and shoulders above all the other moves as the strongest, sharpest and best.” Okay, he's getting carried away there perhaps, but 5...b5 certainly very interesting.
The critical reply – indeed, the only good reply – is 6 Bf1!. Against this, Ulvestad originally proposed 6...h6 but later discarded it, albeit for the wrong reasons (7 Nxf7! Kxf7 8 dxc6 Bc5 9 Be2! is why this isn't any good). 6...Nd4 7 c3 Nxd5, transposing to the Fritz Variation (5...Nd4), has its drawbacks too (such as 8 cxd4! Qxg5 9 Bxb5+ Kd8 10 0-0).
Ulvestad's second idea, 6...Nxd5!? 7 Bxb5 Bb7, looks rather more promising. For example, 8 d4 exd4 9 Qxd4? Qe7+ 10 Qe4 Qxe4+ 11 Nxe4 0-0-0 12 Bxc6 Bxc6 (Ulvestad) is good for Black, since 13 Ng5 f6! 14 Nf7 loses quickly to 14...Bb4+ and ...Rhe8.
Taking the d4-pawn is clearly premature here. White should just castle: 9 0-0 “etc” (Tartakower). This is generally regarded as a refutation of 6...Nxd5, following analysis by GM Reuben Fine: 9...Be7 10 Qh5 g6 11 Qh6 Qd7
12 Qg7 0-0-0 13 Qxf7 (Fine), when White has regained, and appears to have consolidated, the extra pawn: 14 Ne6 is a threat, or if 13...Rhf8 then 14 Qe6 swaps the queens off. So it is somewhat surprising to discover that the engines think that Black is better, casually throwing out the disruptive 14...Ne3!. Well, splendid!
White is not obliged to play 12 Qg7?!. Instead, D.Pena-C.Fonseca, Pamplona 2012, saw 12 Re1 0-0-0 13 Nxf7 Bb4 14 Nxd8 Bxe1, and here 15 Nxb7 Kxb7 16 Bd2 would have been very good for White.
But once again the engines are ready with an improvement: the nonchalant 12...a6!, intending 13 Ba4 Qf5. I think it might be difficult to decide upon this over the board. The main point is that 12...Qf5? gets hit by 13 Bd3, but that's impossible once the bishop has retreated to a4.
Many possibilities arise from White's options at moves 13 and 14 (and move 17 too), but in all of them the activity of Black's pieces provides excellent compensation for the pawn, even into the ending. The game below is a case in point, where I forced the queens off (with 18...Bf8) just to see how easily it might be defended. As it turned out, I didn't have much trouble at all.
I should also add that my opponent also managed to draw as Black, this time after
6...Qxd5!? 7 Nc3 Qc5. It seems there are still plenty of secrets to be uncovered in these old Open Games.
